Source-Matched Microlens Diffuser for Low Speckle Illumination

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Solution Overview

Problem

Coherent light source arrays, such as VCSELs, produce speckle patterns when combined with beam-shaping diffusers, leading to a grainy appearance that is undesirable in certain applications, and existing methods to reduce speckle often require dynamic configurations or increased complexity.

Innovation Solution

A static configuration using a light source array with individually coherent but mutually incoherent emitters paired with a diffuser featuring a random distribution of microlenses, where each microlens acts as a scattering unit to minimize interference and speckle contrast by aligning each light source with a single microlens, eliminating complex amplitude interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If a coherent light source array is combined with a beam-shaping diffuser, then beam shaping and illumination control are achieved, but speckle patterns with high contrast variation are produced

Engineering Contradiction:

Improvebeam shapeVSAvoidspeckle contrast

Core Design Contradiction:

ShapeVSObject-generated harmful factors

Solution Approach 1:

The diffuser is segmented into multiple microlenses, each acting as an independent scattering element. Each microlens is aligned with a corresponding light source emitter, creating separate optical paths that prevent interference between different sources. This segmentation approach maintains beam shaping capability while eliminating speckle contrast variation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each microlens in the diffuser is designed with specific local optical properties to shape the beam from its corresponding light source. The local quality of each microlens-mirror-emitter combination is optimized to provide uniform illumination in the final image plane while preventing speckle formation through localized interference elimination.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If motion is introduced to reduce speckle contrast through averaging effects, then speckle visibility is reduced, but system complexity and space requirements increase

Engineering Contradiction:

Improvespeckle contrastVSAvoidsystem complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the source of speckle interference by removing the coherent correlation between light sources and diffuser elements. By aligning each emitter with a dedicated microlens and ensuring mutual incoherence, the harmful interference term is completely removed from the optical system, avoiding the need for motion-based averaging.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using motion to average speckle patterns, the invention inverts the approach by designing a static system where speckle is prevented from forming in the first place. The microlens array is configured to transform coherent light from multiple incoherent sources into a uniform distribution without creating interference patterns.

Inventive Principle:

Principle #13The other way round (Inversion)

3Illumination intensity

If multiple coherent light sources are used to increase illumination intensity, then brightness is improved, but speckle patterns become more distinct

Engineering Contradiction:

ImprovebrightnessVSAvoidspeckle distinctness

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

Multiple coherent light sources are merged through the microlens array in a way that preserves their individual incoherence. Each light source is coupled to a separate microlens, and the combined output from all microlenses produces uniform illumination. The merging process maintains high brightness while the independence of each source-microlens pair prevents speckle distinctness.

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 approach effectively reduces speckle contrast in a static setup, providing a uniform image by ensuring each light source interacts with a distinct microlens, minimizing the grainy appearance associated with coherent illumination.

Implementation Method 1

A diffuser matched to a light source array to provide illumination with reduced speckle... a diffuser featuring a random distribution of microlenses... each microlens acts as a scattering unit

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

each microlens includes a scattering unit... each microlens acts as a scattering unit to minimize interference and speckle contrast

Methodology Applied

Scientific EffectScattering: Scattering

Data Source

PatentUS20250093015A1Source-matched diffuser for low speckle illumination

Publication Date: 2025.03.20 VIAVI SOLUTIONS INC(US)

AI summary

A diffuser is disclosed. A system comprising a light source and a diffuser is disclosed. The light source is aligned with a microlens of the diffuser in a static configuration. A method of reducing speckle with the system is also disclosed.