IR Barrier Layer for Image Sensor Ghost Image Reduction

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Solution Overview

Problem

Image sensors with dual visible and near-infrared capabilities suffer from IR ghost images due to IR radiation reflection from the redistribution layer, leading to noise and reduced sensitivity.

Innovation Solution

Incorporating an IR reflection layer, IR absorption layer, or a multi-functional isolation layer between the photosensing element and the redistribution layer to prevent IR radiation from impinging on the redistribution layer, thereby eliminating ghost images.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the sensor is made sensitive to NIR range (750-1400 nm) for night vision capability, then the night vision performance is improved, but IR ghost images are created that reduce sensitivity and introduce noise

Engineering Contradiction:

Improvenight vision capabilityVSAvoidIR ghost images

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

An IR barrier layer is introduced as an intermediary component between the photosensing element and the redistribution layer. This layer selectively blocks IR radiation wavelengths (750-1400 nm) from reaching the redistribution layer, preventing the formation of ghost images while allowing the sensor to maintain its dual-mode visible and NIR sensing capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The IR barrier layer is positioned specifically at the location where IR radiation interacts with the redistribution layer to create ghost images. By applying the barrier function locally at this critical interface rather than throughout the entire sensor structure, the solution prevents ghost images while preserving overall sensor sensitivity and functionality

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If the sensor operates in dual mode (visible and IR) to function in both daylight and night vision, then the versatility is improved, but IR radiation is reflected by the redistribution layer creating noise

Engineering Contradiction:

Improvedual-mode capabilityVSAvoidreflected IR radiation

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The IR barrier layer converts the harmful reflected IR radiation into a beneficial blocking action. By preventing IR radiation from reaching the redistribution layer, the layer eliminates the source of ghost images and noise, allowing the sensor to maintain dual-mode operation without the adverse effects of IR reflection

Inventive Principle:

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

Solution Approach 2:

The barrier layer acts as a mediator that separates the photosensing element from the redistribution layer specifically for IR radiation. This intermediary structure allows visible light to pass through unaffected while blocking IR radiation, enabling dual-mode operation without ghost image interference

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

The solution effectively reduces or eliminates IR ghost images, enhancing the sensitivity and image quality of image sensors by preventing IR radiation from contributing to the image formation.

Implementation Method 1

An IR reflection layer is disposed between the photosensing element and the RDL, said IR reflection layer reflecting a reflected portion of the IR radiation back to the photosensing element such that the reflected portion of the IR radiation does not impinge upon the RDL

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

An IR absorption layer is disposed between the photosensing element and the RDL, IR absorption layer absorbing the IR radiation such that a substantial portion of the IR radiation does not impinge upon the RDL

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Implementation Method 3

An isolation layer is disposed between the photosensing element and the RDL, the isolation layer being adapted to absorb the IR radiation such that a substantial portion of the IR radiation does not impinge upon the RDL

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Implementation Method 4

An IR barrier layer is disposed between the photosensing element and the RDL, said IR barrier layer preventing the IR radiation from impinging upon the RDL

Methodology Applied

Scientific EffectElectromagnetic radiation blocking: Absorption (EM radiation)

Data Source

PatentUS9406716B2Infrared reflection/absorption layer for reducing ghost image of infrared reflection noise and image sensor using the same

Publication Date: 2016.08.02 OMNIVISION TECHNOLOGIES INC

AI summary

An image sensor includes a photosensing element for receiving infrared (IR) radiation and detecting the IR radiation and generating an electrical signal indicative of the IR radiation. A redistribution layer (RDL) is disposed under the photosensing element, the RDL comprising pattern of conductors for receiving the electrical signal. An IR reflection layer, an IR absorption layer or an isolation layer is disposed between the photosensing element and the RDL. The IR reflection layer, IR absorption layer or isolation layer provides a barrier to IR radiation such that the IR radiation does not impinge upon the RDL. As a result, a ghost image of the RDL is not generated, resulting in reduced noise and improved sensitivity and performance of the image sensor.