Laser Array Wavelength Diversity for Speckle Reduction
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Solution Overview
Problem
The high coherence of laser beams leads to the speckle effect in laser display, which deteriorates the quality of projected images, as existing methods primarily address spatial coherence and fail to effectively reduce temporal coherence, limiting the effectiveness of speckle cancellation.
Innovation Solution
A laser array is designed with adjacent lasers emitting in the same color but with different wavelengths, reducing temporal coherence and speckle effect by spacing their wavelengths by at least 1 nm, and optionally including additional lasers in different colors to further reduce coherence and enhance color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser beams with high coherence are used, then laser display functionality is achieved, but speckle effect occurs deteriorating image quality
Solution Approach 1:
The patent divides a single laser beam into multiple laser beams with different wavelengths (e.g., multiple blue wavelengths around 470nm, multiple red wavelengths around 630nm, multiple green wavelengths around 530nm). Each wavelength component has reduced temporal coherence relative to the original single wavelength, and their superposition further reduces the overall temporal coherence, thereby reducing the speckle effect while maintaining laser display functionality
Solution Approach 2:
The patent changes the wavelength parameter of the laser beams by using multiple lasers emitting at different wavelengths within the same color range. This parameter change reduces the temporal coherence of individual beams and their combined output, effectively reducing the speckle effect while preserving the color characteristics needed for display
2Object-affected harmful factors
If existing methods address spatial coherence, then some speckle reduction is achieved, but temporal coherence remains high limiting effectiveness
Solution Approach 1:
The patent directly addresses temporal coherence by changing the wavelength parameter - using multiple lasers with different wavelengths (e.g., 465nm, 470nm, 475nm for blue) rather than a single wavelength. This parameter change fundamentally reduces temporal coherence since temporal coherence is inversely related to spectral width, making existing spatial coherence methods supplementary rather than primary
3Object-affected harmful factors
If multiple lasers with different wavelengths are used, then temporal coherence is reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple lasers with different wavelengths into a single integrated laser array structure that emits combined laser beams. The multiple wavelength components are spatially arranged and optically combined, allowing the system to achieve reduced temporal coherence through wavelength diversity while presenting a unified device interface that manages complexity
4Object-affected harmful factors
If wavelength spacing of at least 1 nm is maintained, then speckle reduction is effective, but color gamut may be limited
Solution Approach 1:
The patent optimizes the wavelength parameter by selecting multiple wavelengths within specific ranges (blue: 465-475nm, red: 625-635nm, green: 525-535nm) with spacing of at least 1nm. This parameter selection achieves sufficient temporal coherence reduction for speckle mitigation while keeping wavelengths close enough to maintain pure color perception and wide color gamut
Solution Approach 2:
The patent extends the solution from single-wavelength to multi-wavelength within the same color region, adding spectral dimensionality. By distributing multiple wavelengths within narrow bands (e.g., three blue wavelengths spaced by 1-5nm each), it achieves speckle reduction through spectral diversity while maintaining color purity through tight spectral confinement
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 effectively reduces the speckle effect and improves image quality by minimizing temporal coherence between adjacent laser beams, while also allowing for high color gamut output.
Implementation Method 1
A laser array includes at least one line of lasers comprising a first laser and a second laser which are adjacent. A first laser beam emitted by the first laser and a second laser beam emitted by the second laser are both in a first color, and the first laser beam has a wavelength less than that of the second laser beam.
Data Source
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AI summary
A laser array includes at least one line of lasers. The at least one line of lasers includes a first laser and a second laser which are adjacent. A first laser beam emitted by the first laser and a second laser beam emitted by the second laser are both in a first color, and the first laser beam has a wavelength less than that of the second laser beam.