Nested Unit Pixel Layout for HDR Optical Center Consistency

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Solution Overview

Problem

Conventional CMOS image sensors face challenges in high dynamic range imaging due to inconsistencies in optical centers and increased complexity and cost from having both large and small photodiodes within a unit pixel, leading to artifacts and manufacturing difficulties.

Innovation Solution

A unit pixel design with a smaller photoelectric conversion element surrounded by a larger one, sharing a common micro-lens and color filter, ensuring consistent optical centers and reducing interference, thereby improving image quality and simplifying fabrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If both large and small photodiodes are positioned within the same unit pixel to achieve HDR imaging, then high dynamic range imaging capability is improved, but optical center inconsistency and artifact occurrence increase

Engineering Contradiction:

Improvehigh dynamic range imaging capabilityVSAvoidoptical center consistency

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The small photodiode is positioned inside the hollow interior of the large photodiode, creating a nested configuration where both photoelectric conversion elements share the same optical center. This nesting arrangement allows HDR imaging functionality while eliminating optical center inconsistency artifacts that would otherwise occur with separate positioning of large and small photodiodes.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Adaptability or versatility

If both large and small photodiodes are positioned within the same unit pixel to achieve HDR imaging, then high dynamic range imaging capability is improved, but interference from adjacent unit pixels increases

Engineering Contradiction:

Improvehigh dynamic range imaging capabilityVSAvoidinterference from adjacent unit pixels

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

By nesting the small photodiode within the large photodiode's hollow interior, both elements are contained within a single unit pixel boundary. This configuration prevents light from adjacent unit pixels from interfering with either the large or small photodiode, as the nested structure maintains clear pixel boundaries while enabling dual photoelectric conversion elements.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Productivity

If separate color filters and micro lenses are provided for both large and small photodiodes, then photoelectric conversion efficiency is improved, but fabrication complexity and cost increase

Engineering Contradiction:

Improvephotoelectric conversion efficiencyVSAvoidfabrication complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The large photodiode and small photodiode share common optical components including a single color filter and a single micro lens. This merging approach reduces fabrication complexity and cost by eliminating the need to manufacture and align separate color filters and micro lenses for each photodiode, while still maintaining effective light guidance to both photoelectric conversion elements through the shared optical path.

Inventive Principle:

Principle #5Merging (Combining)

4Productivity

If separate color filters and micro lenses are provided for both large and small photodiodes, then photoelectric conversion efficiency is improved, but manufacturing cost increases

Engineering Contradiction:

Improvephotoelectric conversion efficiencyVSAvoidmanufacturing cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

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 design minimizes artifacts and reduces manufacturing complexity and cost by maintaining optical center consistency and allowing shared micro-lenses and color filters, enhancing image capture across varying luminance levels.

Implementation Method 1

configured to convert incident light into electrical charge

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20250359362A1Unit pixel with multiple photoelectric conversion elements

Publication Date: 2025.11.20 HIMAX IMAGING LIMITED

AI summary

A unit pixel includes a large photoelectric conversion region and a small photoelectric conversion region. The large photoelectric conversion region has a hollow columnar shape, and is configured to convert incident light into a first charge. The small photoelectric conversion region has a columnar shape. The small photoelectric conversion region is surrounded by the large photoelectric conversion region and configured to convert incident light into a second charge.