Concave Microlenses Redirect Leaking Light

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Solution Overview

Problem

Conventional microlens systems in semiconductor imaging devices often fail to redirect light that is not aimed at photosensors due to imperfections in camera lenses and microlenses, resulting in undetected light, especially when light enters at angles or is fanned out beyond the capabilities of the existing microlenses.

Innovation Solution

The implementation of a microlens system that includes both convex and concave plano-convex-shaped microlenses with varying refractive indices and positions to redirect 'leaking' light onto photosensors, using atomic layer deposition (ALD) to form the microlenses and adjust their focal lengths and positions for optimal light capture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional convex microlenses are used to focus light onto photosensors, then on-axis light can be effectively captured, but off-axis light or light entering at angles cannot be redirected and is lost

Engineering Contradiction:

Improvelight capture efficiencyVSAvoidundetected light

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The microlens array is segmented into two distinct types: convex microlenses for capturing on-axis light and concave microlenses for capturing off-axis light. This segmentation allows each lens type to specialize in redirecting specific light paths to photosensors, thereby capturing both on-axis and off-axis light effectively and reducing energy loss from undetected light.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Concave microlenses are introduced to invert the conventional approach by redirecting light from the opposite direction. While convex microlenses focus on-axis light, concave microlenses are positioned to catch off-axis light that would otherwise miss the photosensors, redirecting it from peripheral angles to the sensor surface, thus capturing light that conventional single-type systems lose.

Inventive Principle:

Principle #13The other way round (Inversion)

2Length of moving object

If photosensors are placed closer to the microlens array to improve light capture, then the device profile is reduced, but the photosensors cannot be optimally positioned for light detection

Engineering Contradiction:

Improvedevice profileVSAvoidphotosensor positioning

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The solution moves the photosensors laterally in the plane of the microlens array rather than simply positioning them vertically beneath each microlens. This lateral offset positioning in another dimension allows photosensors to be optimally placed to receive light redirected by both convex and concave microlenses, achieving optimal light detection while maintaining a compact device profile.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If high refractive index materials are used for microlenses to improve light focusing, then light capture efficiency increases, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvelight focusing efficiencyVSAvoidmanufacturing complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent changes the optical parameters of the microlenses by introducing concave shapes with different curvatures and refractive indices. The concave microlenses use lower refractive index materials compared to convex microlenses, and their curved surfaces are optimized to redirect off-axis light effectively. This parameter change allows efficient light capture without requiring all microlenses to use high-refractive-index materials, thereby reducing manufacturing complexity.

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 approach effectively redirects light that would otherwise go undetected, improving image capture by supplementing the role of existing microlenses and allowing for smaller or closer placement of photosensors, while also enabling the use of lower refractive index microlenses, thus enhancing the overall efficiency of light detection.

Implementation Method 1

convex and concave plano-convex-shaped microlenses with varying refractive indices and positions to redirect 'leaking' light onto photosensors

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

using atomic layer deposition (ALD) to form the microlenses

Methodology Applied

Scientific EffectAtomic layer deposition: Physical Vapour Deposition

Data Source

PatentUS7729055B2Method and apparatus providing concave microlenses for semiconductor imaging devices

Publication Date: 2010.06.01 APTINA IMAGING CORP

AI summary

A method and apparatus providing an imaging device with a system of convex and concave microlenses at different levels over an array of photosensors. The concave microlenses redirect leaking light, which is not directed by the convex lenses onto the photosensors, onto the photosensors.