Speckle Reduction in Multi-Laser Scanning Projectors
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Solution Overview
Problem
Scanning projectors using laser light sources often exhibit speckle due to the spatial coherence of laser light, which interferes and creates a sparkling phenomenon when reflected off diffuse surfaces, affecting image quality.
Innovation Solution
The use of multiple laser light sources of the same color, driven alternately to illuminate pixels, lines, or frames, reduces speckle by spatially overlapping light beams with polarization or wavelength diversity, thereby minimizing electrical power consumption and thermal dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple laser light sources are used to reduce speckle, then speckle reduction is achieved, but device complexity increases
Solution Approach 1:
The patent divides the laser light source into multiple independent laser sources (at least two) that operate separately. Each laser source illuminates different pixels, lines, or frames alternately, creating independent speckle patterns that average out to reduce overall speckle visibility in the projected image.
Solution Approach 2:
The patent implements periodic switching between multiple laser sources, where each laser source is activated in alternating time intervals to illuminate different portions of the image. This periodic action ensures that speckle patterns from different sources are temporally separated and spatially overlapped, reducing overall speckle while maintaining continuous illumination.
2Object-affected harmful factors
If multiple laser light sources are driven alternately, then speckle reduction is achieved, but power consumption increases
Solution Approach 1:
The patent employs periodic switching between multiple laser sources where only one or a subset of lasers are active at any given time. This temporal multiplexing ensures that the total power consumption remains comparable to a single laser source, as the duty cycle of each individual laser is reduced proportionally to the number of sources used.
Solution Approach 2:
The patent dynamically controls the activation and deactivation of multiple laser sources based on temporal requirements. The system adjusts which lasers are active at different time intervals, optimizing power distribution across multiple sources while maintaining the same overall illumination level, thereby managing power consumption efficiently.
3Object-affected harmful factors
If multiple laser light sources are used, then speckle reduction is achieved, but thermal dissipation increases
Solution Approach 1:
The patent segments the thermal load across multiple independent laser sources. By distributing the total optical power requirement across at least two separate laser sources that operate alternately, the thermal dissipation from each individual source is reduced proportionally, preventing excessive heat concentration in a single component.
Solution Approach 2:
The periodic switching between multiple laser sources ensures that no single laser operates continuously at full power. Each laser source is activated only during specific time intervals, allowing thermal dissipation to occur during off periods and preventing heat accumulation, thereby managing thermal load effectively across the system.
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 achieves significant speckle reduction while maintaining low power consumption and thermal efficiency, enhancing image quality by up to 0.707 times the reduction factor, depending on the number of laser sources used.
Implementation Method 1
Laser light is spatially coherent, and when reflected off a diffuse surface, the reflected coherent light waves interfere with each other in a regular pattern that results in a user perceiving speckle
Implementation Method 2
The use of multiple laser light sources of the same color, driven alternately to illuminate pixels, lines, or frames, reduces speckle by spatially overlapping light beams with polarization or wavelength diversity
Data Source
AI summary
A scanning projector includes one or more scanning mirrors that reflect a light beam to create an image. The beam is created by multiple laser light sources, at least two of which create light at substantially the same color. The multiple laser light sources are used alternately to illuminate successive pixels, lines, and/or frames. Speckle reduction is achieved because of spatial overlap of the light beams produced by the multiple laser light sources.