Multi-layer Color Filter Array for Image Sensors

Solution Overview

Problem

Existing infrared filters in image sensors face a trade-off between high infrared transmittance and low visible wavelength blocking, leading to either high signal-to-noise ratio (SNR) with significant color errors for small pixel sizes or low SNR with minimal color errors for larger pixel sizes.

Innovation Solution

A multi-layer color filter array is introduced, comprising an invisible-wavelength layer and a visible-wavelength layer, where each filter in the visible-wavelength layer is optically coupled to a corresponding filter in the invisible-wavelength layer, allowing for optimal separation and transmission of infrared and visible light components, thereby improving SNR while minimizing color errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If pigment-based infrared filters are used, then infrared transmittance is improved and SNR is increased, but visible wavelength blocking deteriorates and color error increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidcolor error

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The filter is divided into two distinct layers: a first layer for blocking visible wavelengths (blue and red) and a second layer for transmitting infrared wavelengths. This segmentation allows each layer to be optimized for its specific function, with the visible blocking layer achieving complete visible rejection and the infrared layer achieving high infrared transmittance, thereby resolving the contradiction between color accuracy and SNR

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite structure combining two different filter materials with complementary properties. The first layer uses materials optimized for visible wavelength blocking, while the second layer uses materials optimized for infrared transmission. This composite approach enables the filter to simultaneously achieve both complete visible blocking (minimizing color error) and high infrared transmittance (maximizing SNR)

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If C-based infrared filters are used, then visible wavelength blocking is improved and color error is reduced, but infrared transmittance deteriorates and SNR decreases

Engineering Contradiction:

Improvecolor errorVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The filter is divided into two distinct layers: a first layer for blocking visible wavelengths (blue and red) and a second layer for transmitting infrared wavelengths. This segmentation allows each layer to be optimized for its specific function, with the visible blocking layer achieving complete visible rejection and the infrared layer achieving high infrared transmittance, thereby resolving the contradiction between color accuracy and SNR

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite structure combining two different filter materials with complementary properties. The first layer uses materials optimized for visible wavelength blocking, while the second layer uses materials optimized for infrared transmission. This composite approach enables the filter to simultaneously achieve both complete visible blocking (minimizing color error) and high infrared transmittance (maximizing SNR)

Inventive Principle:

Principle #40Composite materials

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 multi-layer color filter array enhances the signal-to-noise ratio in image sensors by effectively blocking infrared wavelengths while allowing visible light to pass, reducing color errors across various pixel sizes, thereby improving image quality.

Implementation Method 1

A multi-layer color filter array is introduced, comprising an invisible-wavelength layer and a visible-wavelength layer, where each filter in the visible-wavelength layer is optically coupled to a corresponding filter in the invisible-wavelength layer, allowing for optimal separation and transmission of infrared and visible light components

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS9671537B2Multi-layer color filter for low color error and high SNR

Publication Date: 2017.06.06 OMNIVISION TECHNOLOGIES INC

AI summary

Embodiments are described of a color filter array including a plurality of tiled minimal repeating units. Each minimal repeating unit includes an invisible-wavelength filter layer including a plurality of filters and a visible-wavelength filter layer positioned on the invisible-wavelength filter layer and having a plurality of filters such that each filter from the visible-wavelength layer is optically coupled to a corresponding filter in the invisible-wavelength layer.