Polymer-Free Liquid Crystal Diffusers for Laser Speckle Reduction
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Solution Overview
Problem
Existing methods for reducing laser speckles involve mechanical components that increase complexity, weight, and optical path length, which are unsuitable for compact applications like micro projection units.
Innovation Solution
A system using optical diffuser elements with a polymer-free cholesteric liquid crystal medium, controlled by a voltage source and controller, toggles between diffusing and non-diffusing states to reduce laser speckle contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If rotating ground glass diffusers or high frequency oscillating reflective diffusers are used to reduce laser speckles, then laser speckle reduction is achieved, but mechanical complexity, weight, and optical path length increase
Solution Approach 1:
The patent replaces mechanical diffusing systems (rotating ground glass diffusers, oscillating reflective diffusers) with an electronically controllable liquid crystal diffuser. The liquid crystal diffuser uses electrical signals to modulate light diffusion, eliminating mechanical moving parts while achieving speckle reduction through temporal sequencing of multiple diffuser patterns.
Solution Approach 2:
The patent changes the optical parameters of the diffuser by using liquid crystal molecules that can be electrically controlled to alter their orientation and light diffusion characteristics. By changing the liquid crystal state through voltage application, the system dynamically adjusts diffuser patterns without mechanical movement, reducing speckle while maintaining compactness.
2Object-affected harmful factors
If rotating ground glass diffusers or high frequency oscillating reflective diffusers are used to reduce laser speckles, then laser speckle reduction is achieved, but device weight increases
Solution Approach 1:
The patent replaces heavy mechanical diffusing components with a lightweight liquid crystal diffuser that uses electrical fields rather than mechanical motion. The liquid crystal layer is extremely thin and light, controlled by simple electrode patterns, eliminating the need for heavy rotating mechanisms or oscillating mirrors while achieving the same speckle reduction effect.
3Area of moving object
If oscillating mirror implemented as MEMS device is used to reduce laser speckles, then footprint is reduced, but optical path length increases negatively impacting footprint
Solution Approach 1:
The patent replaces the oscillating mirror (even in MEMS form) with a transmissive liquid crystal diffuser. This eliminates the need for reflective optical paths and complex mirror mounting structures, reducing both the lateral footprint and the optical path length. The liquid crystal diffuser can be placed directly in the light path as a thin layer, minimizing additional optical distance.
4Object-affected harmful factors
If mechanical components are used in speckle reduction systems, then speckle reduction is achieved, but reliability decreases due to mechanical complexity
Solution Approach 1:
The patent eliminates mechanical components entirely by using an electrically controlled liquid crystal diffuser. Without moving parts, there are no mechanical failures, wear, or alignment issues. The system achieves speckle reduction through electrical modulation of liquid crystal orientation, dramatically improving reliability while maintaining the desired optical effect.
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 system efficiently and controllably scatters light to reduce laser speckle contrast, maintaining visibility and adaptability across various applications, optimizing speckle reduction and clarity without mechanical parts.
Implementation Method 1
a first optical diffuser element and a second optical diffuser element on the optical path between the laser light source and the illumination target; wherein the controller is operable to toggle the first optical diffuser element and the second optical diffuser element between a diffusing state and a non-diffusing state in a sequential manner independently from each other
Implementation Method 2
one or more optical diffuser elements comprising a polymer free cholesteric liquid crystal medium; and a voltage source connected to the one or more optical diffuser elements; and a controller operatively connected to the laser light source and the voltage source, wherein the controller is operable to apply and remove a driving voltage (Vd) to the one or more optical diffuser elements to toggle the one or more optical diffuser elements between a diffusing state and a non-diffusing state
Data Source
AI summary
Disclosed is system of reducing laser speckle contrast, the system has a laser light source arranged to emit laser light; an illumination target arranged to receive the emitted laser light; a speckle reducer on an optical path between the laser light source and the illumination target, the speckle reducer having one or more optical diffuser elements with a polymer free cholesteric liquid crystal medium; a voltage source connected to the one or more optical diffuser elements; and a controller operatively connected to the laser light source and the voltage source, wherein the controller is configured to apply and remove a driving voltage Vd to the one or more optical diffuser elements to toggle the one or more optical diffuser elements between a diffusing state and a non-diffusing state.