Laser Projection Speckle Mitigation via Lens Displacement
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Solution Overview
Problem
Current projection systems using coherent light sources, such as lasers, suffer from speckle interference that disrupts image continuity due to rough surfaces, leading to undesirable intensity variations, which existing technologies have not effectively mitigated without compromising image quality.
Innovation Solution
The solution involves shifting the image position in-time by translating lens elements orthogonally to the optical axis within the optical train, combined with electronic compensation, to reduce speckle while maintaining image quality, using a projector with a light source, relay lens, and projection lenses, allowing for partial or full pixel shifts to mitigate speckle effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If coherent light sources (lasers) are used in projection systems, then brightness and reliability are improved, but speckle interference appears causing image quality degradation
Solution Approach 1:
The patent applies dynamics by making the optical system movable through vibration or displacement of optical elements (such as diffusers, scramblers, or lens components) along the optical path. This dynamic movement changes the speckle pattern over time, allowing temporal averaging that reduces perceived speckle while maintaining the high brightness benefits of laser sources
Solution Approach 2:
The patent specifically employs mechanical vibration by vibrating optical elements (diffusers, scramblers, or other components) at frequencies typically above human perception thresholds. This vibration continuously alters the light scattering paths, causing the speckle pattern to fluctuate rapidly and average out over time, thereby reducing speckle visibility while preserving laser brightness
2Object-affected harmful factors
If optical elements are moved to reduce speckle, then speckle interference is mitigated, but image stability and focus quality may deteriorate
Solution Approach 1:
The patent applies periodic action by implementing controlled vibration or oscillation of optical elements at specific frequencies. This periodic movement creates a stable temporal average of speckle patterns over time, reducing speckle while maintaining consistent image quality. The periodic nature ensures that focus and image stability are preserved through controlled, repeatable motion cycles
Solution Approach 2:
The patent uses diffusers and scramblers that create multiple scattered light paths, effectively creating copies of the light wavefront that traverse different paths. These copied paths interfere constructively and destructively to form speckle, but when the diffuser/scrambler moves periodically, the copied paths change in a controlled manner that averages out speckle while maintaining image stability
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 in projection systems by shifting the image position, maintaining high image quality and modulation transfer function, suitable for both two-dimensional and three-dimensional projection applications.
Implementation Method 1
a relay lens located in an image path generated by the light source and pixel panel for relaying an intermediate image of the pixel panel
Implementation Method 2
at least one projection lens for projecting intermediate imagery received from the relay lens onto a display screen
Implementation Method 3
shifting of image position in-time to mitigate speckle... a single lens element in the optical train may be translated substantially orthogonally to the optical axis
Implementation Method 4
lasers suffer from the appearance of speckle when laser light is scattered from surfaces with roughness on the order of a wavelength
Implementation Method 5
Speckle forms when coherent, but differently phased, portions of the reflected beam constructively and/or destructively add inside a single resolution spot of the detector
Data Source
AI summary
Disclosed herein are optical projection systems and related methods for projecting imagery employing shifting image position in-time to mitigate speckle. Exemplary optical systems may include a projector having a light source, a relay lens and at least one projection lens for projecting images. The relay lens or the projection lens may have at least one lens element that may be translated in-time substantially orthogonal to the optical axis of the optical system. Alternatively, the projection lens in its entirety may be shifted in-time to reduce speckle. Further, in stereoscopic embodiments, two projection lenses may be employed, wherein at least one element in each projection lens is moveable to shift the image in-time to reduce speckle. Moreover, electronic compensation, such as electronic addressing or image warping, for the image shifting may be employed to shift the image in a direction opposite to the speckle-reducing shift in position.