Laser Diode Diffuser Feedback for VR Speckle Reduction
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Solution Overview
Problem
Speckle patterns degrade image quality in virtual and augmented reality systems using laser light sources due to interference and diffraction, resulting in grainy and distorted images.
Innovation Solution
A diffuser is placed in front of a laser diode to generate a chaotic laser pattern by reflecting a portion of the light beam back into the laser diode, combined with current modulation to induce chaotic operation, reducing coherence and speckle formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser light source is used in projection displays, then the brightness and directionality are improved, but the image quality degrades due to speckle patterns and interference
Solution Approach 1:
The patent introduces dynamic modulation of the laser current to create time-varying optical feedback conditions. By dynamically changing the operating point of the laser through current modulation, the system creates chaotic dynamics that prevent stable speckle pattern formation, thus maintaining brightness while reducing speckle harm
Solution Approach 2:
The patent implements optical feedback by reflecting a portion of the laser output back into the laser cavity through a diffuser. This feedback mechanism, when combined with current modulation, creates chaotic dynamics in the laser operation that reduce coherence and eliminate speckle patterns while preserving the bright laser output
2Speed
If the laser coherence is increased to improve beam quality, then the directionality is improved, but the speckle patterns become more severe
Solution Approach 1:
The patent uses dynamic current modulation to create time-varying conditions in the laser cavity. This dynamic operation prevents the establishment of stable interference patterns while maintaining the coherent beam properties needed for directionality, thus resolving the contradiction between beam quality and speckle severity
Solution Approach 2:
The patent changes the operational parameters of the laser by modulating the drive current and introducing optical feedback. These parameter changes create chaotic dynamics that reduce temporal coherence and eliminate stable interference patterns, maintaining beam directionality while reducing harmful interference
3Object-affected harmful factors
If optical feedback is introduced to create chaotic operation, then the speckle patterns are reduced, but the system complexity increases
Solution Approach 1:
The patent implements a self-service feedback mechanism where the laser system uses its own output as the feedback source. A diffuser reflects a portion of the laser beam back into the cavity, creating autonomous optical feedback that induces chaotic dynamics and reduces speckle without requiring external complex control systems
Solution Approach 2:
The patent introduces a diffuser as an intermediary element to mediate the optical feedback process. The diffuser scatters the reflected light to create distributed feedback throughout the laser cavity, inducing chaotic dynamics and speckle reduction while maintaining relatively simple system architecture
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 chaotic laser pattern reduces speckle patterns, improving image quality by increasing spectral width and reducing coherence, resulting in a more uniform and comfortable virtual reality experience.
Implementation Method 1
A diffuser is placed in front of a laser diode to generate a chaotic laser pattern by reflecting a portion of the light beam back into the laser diode
Implementation Method 2
The diffuser is configured to reflect back a portion of the light beam into the laser diode as reflected light beams
Implementation Method 3
The diffuser is a random pattern or pseudo random pattern surface which causes a plurality of light beam rays to bounce off the different locations of the diffused surface and scatter back into the laser diode
Implementation Method 4
Speckle patterns are a type of intensity pattern produced by the mutual interference of a plurality of wavefronts emanating from a coherent source
Implementation Method 5
interference generated by diffraction at a large number of scattering particles on the projection optics
Implementation Method 6
The laser is also driven further into chaotic operation by a combination of the received optical feedback and the current modulation
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C~2D
AI summary
An imagining system for reducing laser speckling, the imagining system comprising a laser diode (501) to generate a light beam having a wavelength within a visible spectrum; a modulator (505) to vary a current for driving the laser diode (501); and a diffuser (503) to receive the light beam, wherein the diffuser (503) is comprises a random patterned surface or a pseudo-random surface configured to cause a reflected portion of the light beam to bounce off the random patterned surface or the pseudo-random surface and scatter back into the laser diode (501) as reflected rays to generate a chaotic laser pattern, and further to cause a transmitted portion of the light beam to pass therethrough.