Pixel Stack Refractive Index Layout to Reduce Color Mixture

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Solution Overview

Problem

Existing imaging devices face challenges in reducing color mixture between pixels, particularly when oblique light enters the device, leading to unwanted light transmission into adjacent pixels due to the configuration of color filters and refractive indices.

Innovation Solution

The imaging device incorporates a stacked structure with a photoelectric conversion section, a first light transmissive film with a specific refractive index, and a second light transmissive film with a higher refractive index, along with a pixel separation section between adjacent films, which has a lower refractive index, to refract and reflect oblique light, preventing it from entering adjacent pixels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional color filter structure is used, then the device complexity is low, but color mixture between pixels occurs when oblique light enters

Engineering Contradiction:

Improvecolor mixture reductionVSAvoidpixel structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pixel structure is segmented into multiple functional layers: a photoelectric conversion layer, a first light transmissive film with refractive index n1, and a second light transmissive film with refractive index n2 (>n1). This segmentation allows each layer to perform a specific optical function, with the stacked structure creating multiple interfaces that manipulate oblique light paths to prevent color mixture between adjacent pixels

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by assigning different refractive indices to specific layers (n1 for the first light transmissive film, n2 for the second light transmissive film where n2>n1). This localized variation in optical properties creates specific refraction and reflection characteristics at each interface, enabling the structure to selectively guide oblique light away from adjacent pixels while maintaining normal light transmission

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If light enters obliquely, then the imaging device can capture a wider field of view, but light may enter adjacent pixels causing color mixture

Engineering Contradiction:

Improvelight entry angle rangeVSAvoidcolor accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent converts the harmful effect of oblique light entry (which causes color mixture) into a beneficial effect by utilizing refraction and total internal reflection at the interfaces between layers with different refractive indices. The stacked structure with n1<n2 creates specific angle-dependent optical paths that redirect oblique light back toward the originating pixel or away from adjacent pixels, thereby improving color accuracy while maintaining wide field of view capability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the optical parameters (refractive indices) of the light transmissive films to control light propagation. By setting n2>n1, the structure creates specific critical angles for total internal reflection at the interfaces, which dynamically redirects oblique light based on its incident angle, thereby maintaining color accuracy across a wide range of viewing angles

Inventive Principle:

Principle #35Parameter changes

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 effectively reduces color mixture by ensuring that oblique light is totally reflected at the interface, minimizing light leakage between pixels and improving image quality.

Implementation Method 1

an angle of the entry into a wall side of the first light transmissive film is made shallow (an entry angle with respect to an interface between the first light transmissive film and an inter-pixel light-blocking section is made large) by the second light transmissive film having a high refractive index

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

the light is totally reflected at the interface

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS12183755B2Imaging device and electronic apparatus

Publication Date: 2024.12.31 SONY SEMICON SOLUTIONS CORP

AI summary

An imaging device and an electronic apparatus that make it possible to reduce color mixture between pixels are provided. An imaging device of an embodiment of the present disclosure includes: a plurality of pixels (PX) each having a stacked structure in which a photoelectric conversion section (PD) including a light entrance surface, a first light transmissive film provided to face the light entrance surface and having a first refractive index (nCF), and a second light transmissive film having a second refractive index (n18) higher than the first refractive index are stacked in order in a stacking direction, the plurality of pixels being arranged in an in-plane direction orthogonal to the stacking direction; and a first pixel separation section provided between a plurality of the first light transmissive films adjacent to each other in the in-plane direction, and having a third refractive index (n13) lower than the first refractive index.