Microrefractive Element Stabilized Laser Array Speckle Reduction
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Solution Overview
Problem
Conventional laser-based imaging systems face limitations due to speckle, which reduces contrast and resolution, and existing methods to mitigate speckle often require moving parts, complex optical arrangements, or low light-collection efficiencies, making them unsuitable for high-resolution, dynamic imaging applications.
Innovation Solution
A light source comprising a microresonator with opposing mirrors and an array of microrefractive elements that stabilize the resonator and produce a microlaser beam array, allowing for the incoherent combination of hundreds or thousands of microlaser beams to reduce speckle and enable high-resolution, pulsed imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional laser is used as a light source in high-resolution imaging, then the imaging system achieves high intensity and coherence, but speckle limits the contrast and resolution of the obtained images
Solution Approach 1:
The patent divides a single laser beam into multiple independent microlaser beams by placing an array of microrefractive elements (such as microlenses or microprisms) in the laser cavity. Each microrefractive element creates a separate microlaser beam with random phase and polarization, and these beams are incoherent with each other, thereby eliminating speckle while maintaining high intensity
Solution Approach 2:
The patent introduces local variations in the laser cavity by placing microrefractive elements at specific positions, where each element creates a microlaser beam with unique local properties (phase, polarization, direction). This local differentiation ensures that the combined output has reduced coherence and eliminated speckle while preserving overall high intensity
2Measurement precision
If a rotating diffuser is used to reduce speckle, then the intensity variations are averaged over time, but moving parts are required and the integration time must be sufficiently long
Solution Approach 1:
The patent replaces the mechanical rotating diffuser system with a stationary array of microrefractive elements. Instead of mechanically moving a single diffuser to average speckle over time, the system uses multiple fixed microlaser beams with random phases and polarizations that inherently produce speckle-free illumination, eliminating all moving parts
Solution Approach 2:
The patent uses pulsed laser operation where each pulse generates a new set of microlaser beams with random phases. The periodic pulsing ensures that each pulse contributes independently to the image formation, achieving speckle reduction without requiring temporal averaging over long integration times, thus enabling imaging of dynamic objects
3Measurement precision
If chaotic cavities or random lasers are used to reduce speckle, then speckle-free imaging is achieved, but light-collection efficiencies are low and divergence of emitted radiation is high
Solution Approach 1:
The patent segments the laser cavity into multiple independent microlaser regions, each contributing a controlled microlaser beam. This segmentation allows for efficient light collection from each microregion while maintaining incoherence between beams, avoiding the low efficiency associated with chaotic cavities
Solution Approach 2:
The patent controls the emission characteristics of microlaser beams in the angular dimension by using microrefractive elements with specific focal lengths and positions. This dimensional control ensures low divergence and efficient light collection, contrasting with the high divergence of random lasers while maintaining speckle-free operation
4Quantity of substance
If VCSEL arrays are used to reduce speckle, then multiple laser beams are produced, but diffraction losses are high and array geometry is limited
Solution Approach 1:
The patent introduces microrefractive elements as intermediary components within the laser cavity that focus and direct the formation of microlaser beams. These intermediaries reduce diffraction losses by confining the optical modes within the cavity, allowing efficient extraction of multiple beams without the high diffraction losses inherent in VCSEL arrays
Solution Approach 2:
The patent changes the geometric parameters of the laser cavity by incorporating microrefractive elements with varying focal lengths, positions, and orientations. This parameter variation enables flexible control over the number, direction, and properties of microlaser beams, overcoming the geometric limitations of VCSEL arrays while minimizing diffraction losses through optimized cavity design
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 eliminates speckle while maintaining high contrast and allowing for short-duration imaging of dynamic objects, achieving improved image quality and flexibility in array geometry, suitable for various gain media and imaging applications.
Implementation Method 1
An array of microrefractive elements is arranged within the resonator so as to stabilize the resonator and produce a microlaser beam for each microrefractive element in the array
Implementation Method 2
A microresonator having opposing mirrors arranged substantially parallel to one another
Implementation Method 3
A laser gain medium is situated between the opposing mirrors
Data Source
AI summary
A light source for an imaging system. The light source includes a microresonator laser array having opposing mirrors arranged substantially parallel to one another. A laser gain medium is between the opposing mirrors. An array of microrefractive elements is arranged to stabilize the microresonator. A pump laser's output is shaped by a lens that directs it toward the micro-resonator laser array. An output lens directs a plurality of laser beams from the microresonator laser array to be incoherently combined at an object to be illuminated.