Laser Module Speckle Reduction via Polarization Splitting
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Solution Overview
Problem
Laser projectors face the challenge of the speckle effect, which results from interference between laser beams and the projection surface, leading to uneven light spots, and high modulation rates required to reduce this effect are not easily integratable into consumer devices due to narrow spectral line widths.
Innovation Solution
A laser module that combines laser beams from multiple sources with different polarizations using mirror devices and beam splitters to create an overall laser beam, allowing for efficient reduction of the speckle effect by splitting and recombining laser beams with altered polarizations, specifically utilizing blue, red, and green laser diodes and polarization-dependent beam splitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high modulation rates (several 100 MHz to 1 GHz) are used to reduce the speckle effect, then the speckle contrast ratio is reduced to an acceptable level, but the narrow base spectral line width makes high modulation rates difficult to integrate into consumer devices
Solution Approach 1:
The laser beam from the second laser light source is divided into two separate paths: a main path and a splitting path. This segmentation allows the beam to be manipulated differently in each path, enabling speckle reduction through polarization changes without requiring high modulation rates that would be difficult to integrate into consumer devices.
Solution Approach 2:
The invention changes the polarization state of the laser beam in the splitting path using a half-wave plate, while maintaining the original polarization in the main path. This parameter change (polarization state) enables the reduction of speckle contrast ratio without requiring high modulation rates, thus avoiding integration difficulties in consumer devices.
2Object-affected harmful factors
If laser beams from multiple sources are combined to reduce the speckle effect, then the speckle contrast ratio is reduced, but the device complexity increases due to additional mirror devices and beam splitters
Solution Approach 1:
The invention combines the laser beams from three different laser light sources (blue, red, and green) into a single overall laser beam using mirror devices and a beam splitter. This merging approach reduces the speckle contrast ratio by combining multiple coherent sources while managing the complexity through efficient optical path integration.
Solution Approach 2:
The beam splitter serves multiple functions: it combines the laser beams from different sources and simultaneously directs them through appropriate optical paths. This multi-functionality reduces the need for separate components for each function, thereby managing device complexity while achieving speckle reduction.
3Object-affected harmful factors
If the laser beam of the second laser light source is split into main path and splitting path with polarization change, then the speckle effect is reduced, but the alignment precision requirements increase
Solution Approach 1:
A half-wave plate is introduced as an intermediary element in the splitting path to change the polarization state of the laser beam. This intermediary component enables precise control over the polarization angle, facilitating accurate alignment and reducing the speckle effect while providing a manageable interface for alignment adjustments.
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 the speckle contrast ratio, enabling the generation of bright, uniform images on a projection surface with minimal speckle effect, using fewer elements and allowing for precise mechanical adjustment of laser beams for optimal alignment.
Implementation Method 1
the polarization of the laser beam of the second laser light source being changed from the first polarization to the second polarization in a splitting path
Implementation Method 2
the laser beams of the first and the third laser light sources being coupled into the overall laser beam with the aid of mirror devices
Implementation Method 3
a 50/50 beam splitter which has a surface, facing the first laser light source, having a wavelength-dependent coating which is totally reflective for the first laser light source
Data Source
AI summary
A laser module includes a first laser light source, a second laser light source, and a third laser light source. Laser beams of the laser light sources are combinable into an overall laser beam. The laser beam of the first laser light source and the laser beam of the second laser light source have a first polarization, and the laser beam of the third laser light source has a second polarization. The laser beams of the first and the third laser light sources are coupled into the overall laser beam with the aid of mirror devices. The laser beam of the second laser light source is split, the polarization of the laser beam of the second laser light source being changed from the first polarization to the second polarization in a splitting path. The laser beam of the second laser light source having the second polarization is coupled into the overall laser beam via the splitting path, and the laser beam of the second laser light source having the first polarization is coupled into the overall laser beam via a main path.