Vibrating Diffuser Speckle Reduction in Laser Projectors
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Solution Overview
Problem
Laser-based image projectors suffer from speckle patterns due to the coherent nature of laser light, which can cause undesired sparkling effects when projected onto non-specular surfaces, degrading the image quality.
Innovation Solution
Incorporation of a despeckle module comprising a microlens array, a diffuser, and an in-plane vibrator, where the diffuser is vibrated to change the phase of the light, effectively reducing speckle patterns by randomizing the interference patterns on the observer's retina.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If laser light source is used in projector, then lifespan and color gamut are improved, but speckle patterns are generated degrading image quality
Solution Approach 1:
The patent applies dynamics by vibrating the diffuser at frequencies between 50-2000 Hz to dynamically modulate the speckle pattern. This temporal variation causes the speckle grains to shift and average out over time, reducing the perceived speckle contrast while maintaining the laser light source's lifespan and color gamut advantages.
Solution Approach 2:
The patent directly applies mechanical vibration to the diffuser element to reduce speckle patterns. The vibrator mechanically oscillates the diffuser, which modulates the coherent laser light and transforms the static speckle pattern into a dynamic one that averages to lower contrast over the integration time of the human eye or camera sensor.
2Object-affected harmful factors
If diffuser is added to reduce speckle, then speckle visibility is reduced, but device complexity increases
Solution Approach 1:
The patent merges the diffuser function with the speckle reduction function into a single integrated component. The diffuser serves dual purposes: illuminating the display element uniformly and reducing speckle patterns when combined with vibration, thereby reducing overall device complexity compared to adding separate diffuser and speckle reduction elements.
Solution Approach 2:
The diffuser element serves itself by performing both illumination diffusion and speckle reduction through vibration. The same optical component that is necessary for uniform illumination also becomes the active element for speckle mitigation when vibrated, eliminating the need for additional dedicated speckle reduction components.
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 significantly reduces the visibility of speckle patterns, resulting in a clearer and more stable projected image by averaging the intensity of speckle, enhancing the overall image quality.
Implementation Method 1
Laser-based image projectors suffer from speckle patterns due to the coherent nature of laser light
Implementation Method 2
Incorporation of a despeckle module comprising a microlens array, a diffuser, and an in-plane vibrator
Data Source
AI summary
A despeckle optical system for an image projector includes a diffuser, an in-plane vibrator, a microlens array, and a vibrator driver. The in-plane vibrator is coupled to vibrate the diffuser along a vibration plane. The vibrator driver is coupled to drive the in-plane vibrator and configured to drive the in-plane vibrator at different vibration amplitudes for averaging the intensity of speckle in display light that propagates through the diffuser via the microlens array.