VCSEL Speckle Reduction via Electro-Optic Nanoantennas
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Solution Overview
Problem
Speckle patterns caused by coherent light sources, such as VCSELs, pose a challenge in imaging applications like facial recognition and driver monitoring, leading to noise in image frames and loss of information in dark regions, particularly in portable, low-power devices where mechanical speckle reduction methods are not feasible.
Innovation Solution
The use of light scattering structures with embedded nanoantennas in electrically responsive materials, such as liquid crystals, that apply time-varying electric signals to dynamically change the refractive index, altering the direction, phase, and polarization of light, thereby reducing speckle interference between coherent light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If VCSELs are used as illumination sources, then beam shaping efficiency and light utilization are improved, but speckle pattern formation occurs due to light coherence
Solution Approach 1:
The patent applies dynamics by making the refractive index of the electro-optic material time-varying through application of time-varying electric signals. This dynamically changes the scattering properties of the light scattering structure, thereby reducing speckle patterns while maintaining efficient beam shaping and light utilization from VCSEL sources.
Solution Approach 2:
The patent changes the refractive index parameter of the electro-optic material by applying time-varying electric signals. This parameter change modifies the optical properties of the light scattering structure, enabling it to reduce speckle patterns while preserving the coherent light's beam shaping capabilities.
2Object-generated harmful factors
If mechanical methods like rotating diffuse glass are used to reduce speckle, then speckle reduction is achieved, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces mechanical speckle reduction methods (such as rotating diffuse glass) with an electro-optic approach. By using time-varying electric signals to modulate the refractive index of the electro-optic material, the system achieves speckle reduction without any moving parts, thereby reducing device complexity and power consumption.
Solution Approach 2:
Instead of mechanical movement, the patent changes the optical parameter (refractive index) of the electro-optic material through electric field application. This parameter change provides a non-mechanical means to achieve speckle reduction, suitable for portable and low-power devices.
3Object-generated harmful factors
If time-varying electric signals are applied to electro-optic material, then refractive index changes and light scattering varies to reduce speckle, but energy consumption increases
Solution Approach 1:
The patent employs periodic action by applying time-varying electric signals at specific frequencies to the electro-optic material. This periodic modulation of the refractive index creates time-varying light scattering that reduces speckle patterns. The frequency and duty cycle of the signals can be optimized to balance speckle reduction effectiveness with power consumption.
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 patterns in coherent light sources, enhancing image quality and information retention in imaging applications while maintaining compactness and low power consumption, making it suitable for integration into handheld devices.
Implementation Method 1
application of a time-varying electric signal (e.g., a time varying voltage) can vary the refractive index
Implementation Method 2
Light scattering from the nanoantennas depends on the refractive index of the material in which they are embedded
Implementation Method 3
Speckle can be a consequence of diffuse reflection of coherent radiation from rough surfaces resulting in interference of many waves of the same frequency, each having different phases and amplitudes
Data Source
AI summary
A light emitting device comprises a plurality of coherent light sources, and a plurality of light scattering structures. Each light scattering structure is located in an optical path for light output from a different corresponding one of the coherent light sources. Each light scattering structure comprises an arrangement of nanoantennas embedded in an electrically responsive material and electrical contacts by which to apply a voltage to the electrically responsive material. Application of a time varying electrical signal causes the refractive index of the electrically responsive material in a light scattering structure to vary and thereby varies light scattering by the nanoantennas in the light scattering structure. This effect may be used to reduce speckle caused by interference of light output by the coherent light sources.