Rotating Prism Illumination System Speckle Reduction
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Solution Overview
Problem
Conventional laser projection systems suffer from speckle patterns caused by high coherence, leading to non-uniform brightness and degraded optical quality due to interference phenomena.
Innovation Solution
An illumination system comprising a coherent light source, a light uniforming element, and a rotating prism with an incident polygonal pyramid portion that splits the coherent beam into multiple beams incident on the light uniforming element from different angles, effectively changing the speckle pattern over time due to visual persistence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a coherent light source (laser) is used to provide high brightness and directionality, then illumination intensity and beam quality are improved, but speckle patterns are generated due to interference phenomena causing non-uniform brightness
Solution Approach 1:
The patent introduces a rotating diffuser that dynamically changes the scattering angle and position of light beams over time. This dynamic rotation causes the speckle pattern to move and change continuously, utilizing the persistence of vision effect to average out the speckle intensity distribution, thereby reducing the visibility and impact of speckle patterns while maintaining laser brightness
Solution Approach 2:
The patent adds temporal dimension by rotating the diffuser over time, transforming a static speckle pattern into a dynamic one. The rotation introduces time as a new dimension, allowing multiple speckle patterns to be superimposed within the visual persistence time, effectively reducing speckle contrast through temporal averaging
2Stability of the object's composition
If optical components with slightly uneven surfaces are used in the illumination path, then beam shaping and uniforming are achieved, but speckle patterns are generated due to interference of coherent light
Solution Approach 1:
The rotating diffuser dynamically alters the optical path and scattering characteristics over time, preventing the formation of stable interference patterns. By continuously changing the light distribution, the system maintains beam uniformity while avoiding the generation of persistent speckle patterns that would occur with static optical components
Solution Approach 2:
The diffuser acts as an intermediary element between the coherent light source and the target. It introduces controlled scattering that mediates the coherent light, transforming it into a more diffuse illumination while the rotation of the diffuser prevents the intermediary from creating fixed interference patterns
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
Significantly reduces the speckle phenomenon, resulting in display images with uniform brightness and improved optical quality by superimposing varying speckle patterns observed within a visual persistence time interval.
Implementation Method 1
The prism has a light incident end and a light exit end. The light incident end has at least one incident polygonal pyramid portion protruding away from the light exit end. Moreover, the prism is capable of rotating about an axis, and the axis extends from the light incident end to the light exit end.
Implementation Method 2
due to the high coherence of the laser beam 113, after the laser beam 113 passes through an optical component (such as a lens, a reflector) having a slightly uneven surface in the laser projection apparatus 100, a speckle pattern formed by the laser beam 113 is generated on the screen due to the interference phenomenon of the laser beam 113
Data Source
AI summary
An illumination system including at least one coherent light source, a light uniforming element, and a prism is provided. The coherent light source is capable of emitting a coherent beam. The light uniforming element is disposed on a transmission path of the coherent beam. The prism is disposed on the transmission path of the coherent beam and between the coherent light source and the light uniforming element. The prism has a light incident end and a light exit end. The light incident end has at least one incident polygonal pyramid portion protruding away from the light exit end. The prism is capable of rotating about an axis, and the axis extends from the light incident end to the light exit end. The illumination system effectively reduces the degree of the speckle phenomenon.