Optoelectronic Module Speckle Reduction via Diffuser and Fresnel Lens
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Solution Overview
Problem
Existing light-emitting optoelectronic modules that generate coherent light struggle with speckle noise when illuminating objects with rough surfaces, particularly when the distance between the module and the surface changes over time, requiring elongated exposure times and resource-intensive methods to average out the noise.
Innovation Solution
A light-emitting optoelectronic module comprising a coherent light source, a diffuser with a specific divergence angle, and a Fresnel lens element with an array of Fresnel rings, where the path difference between the diffuser and the Fresnel lens is significantly larger than the coherence length, generating a diffuse emission with reduced speckle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffuser is positioned in front of a coherent light source and rotated while the image is being collected, then noise originating from speckle can be averaged out over time in the collected image, but the exposure time is elongated and power resources are consumed
Solution Approach 1:
The patent segments the coherent beam into multiple sub-beams using a diffuser, creating multiple independent speckle patterns that can be combined to reduce overall speckle noise. This allows immediate exposure without requiring temporal averaging through rotation or modulation.
Solution Approach 2:
The patent introduces a Fresnel lens as an intermediary optical element between the diffuser and the target. This lens focuses the diffused light while maintaining the reduced speckle effect, enabling both immediate exposure and high image quality without requiring mechanical rotation or extended exposure times.
2Measurement precision
If frequency modulation or other components are used to average out speckle, then noise due to speckle can be averaged out over time, but power resources are consumed
Solution Approach 1:
The patent segments the coherent beam into multiple sub-beams using a diffuser, creating multiple independent speckle patterns that can be combined to reduce overall speckle noise. This spatial segmentation eliminates the need for temporal modulation and associated power consumption.
Solution Approach 2:
The patent replaces mechanical rotation or frequency modulation systems with a static optical arrangement comprising a diffuser and Fresnel lens. This substitution eliminates moving parts and active modulation, thereby reducing power consumption while achieving speckle reduction.
3Adaptability or versatility
If the distance between a light-emitting optoelectronic module and the rough surface changes over time, then speckle appears as temporal noise in captured images, but maintaining fixed distance limits adaptability
Solution Approach 1:
The patent segments the coherent beam into multiple sub-beams using a diffuser, creating multiple independent speckle patterns. When the distance changes, these segmented beams maintain their independence, allowing the system to adapt to distance variations while the Fresnel lens ensures proper focusing and maintains image quality.
Solution Approach 2:
The patent creates a dynamic system where the diffuser and Fresnel lens work together to maintain effective illumination and reduced speckle across varying distances. The optical arrangement adapts to distance changes without requiring active control or mechanical adjustment, preserving both adaptability and image quality.
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
Enables immediate exposure and reduced resource consumption while minimizing speckle noise in images captured, allowing for efficient illumination and imaging without the need for prolonged exposure times.
Implementation Method 1
a diffuser operable to generate a diffuse emission
Implementation Method 2
The path difference is larger than the coherence length
Implementation Method 3
a Fresnel lens element... generates an emission with reduced speckle
Implementation Method 4
The Fresnel lens element includes an array of Fresnel rings
Data Source
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AI summary
Light-emitting optoelectronic modules operable to generate an emission characterized by reduced speckle can include a coherent light source, a diffuser, and a Fresnel element. The coherent light source is operable to generate a coherent emission, characterized by a coherence length, incident on the diffuser. The diffuser is characterized by a divergence angle. The divergence angle is the angle between a first path-length from the diffuser to a Fresnel element and a second path-length from the diffuser to the Fresnel element, wherein their difference defines a path difference. In some instances, the path difference is substantially larger than the coherence length.