Rotating Diffuser for Laser Projection Interference Reduction
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Solution Overview
Problem
Current digital cinema projection systems face challenges in achieving high brightness and uniformity while maintaining cost-effectiveness, due to limitations in etendue matching, laser speckle artifacts, and interference issues with coherent light sources.
Innovation Solution
A laser projection system that includes a coherent light source, an optical integrating system, and a randomizing optical element that spatially moves over time to temporally randomize the phase, angle, or spatial location of the coherent light, forming a uniformized laser light image for projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser sources are used for digital cinema projection, then brightness and color purity are improved, but interference artifacts and speckle are generated
Solution Approach 1:
The patent segments the coherent laser beam into multiple spatial modes using a rotating diffuser, which divides the single coherent source into many incoherent beamlets. This segmentation destroys the spatial coherence that causes interference artifacts while preserving the total light intensity for brightness.
Solution Approach 2:
The patent introduces dynamic motion through a rotating diffuser element that continuously changes the spatial distribution of the laser beam. This temporal dynamics ensures that interference patterns change faster than the camera exposure time, effectively averaging them out and eliminating visible artifacts.
2Stability of the object's composition
If optical integrating systems are used to uniformize laser light, then illumination uniformity is improved, but interference artifacts are enhanced
Solution Approach 1:
The patent places the diffuser in the rotating element position within the optical integrating system, making the integration process dynamic. This rotation ensures that while uniformity is achieved through integration, the continuous change in phase relationships prevents stable interference patterns from forming.
Solution Approach 2:
The rotating diffuser creates periodic modulation of the laser beam at frequencies above the camera's temporal resolution. This periodic action ensures that interference patterns are continuously refreshed and averaged out, while the integration process maintains illumination uniformity over the exposure period.
3Quantity of substance
If high etendue optical systems are used, then light throughput is improved, but system complexity and cost increase
Solution Approach 1:
The patent changes the coherence parameter of the laser light by introducing a rotating diffuser, transforming coherent light into partially coherent light. This parameter change allows the system to achieve high light throughput without requiring complex high-etendue optical paths, as the reduced coherence tolerates tighter optical tolerances.
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 reduces interference artifacts and achieves high brightness and uniformity in projected images, allowing for efficient use of single or multiple laser sources without visible interference, and simplifies the optical system by reducing etendue requirements.
Implementation Method 1
a randomizing optical element configured to spatially move over time in order to temporally randomize the phase, angle or spatial location of coherent light it receives
Implementation Method 2
an optical integrating system configured to uniformize coherent light it receives
Data Source
AI summary
A laser projection system comprising a laser source system configured to emit coherent light, an optical integrating system configured to uniformize coherent light it receives, a randomizing optical element configured to spatially move over time in order to temporally randomize the phase, angle or spatial location of coherent light it receives, an image forming system configured to interact with laser light that has been both uniformized by the optical integrating system and randomized by the randomizing optical element, thereby forming a laser light image, and a projection system configured to project the laser light image onto a viewing screen.