Laser Projection Speckle Reduction via Phase Shifting and Optical Integration
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Solution Overview
Problem
Current digital projection systems face challenges in achieving high brightness, uniformity, and speckle-free imaging for digital cinema applications, with existing technologies being costly, complex, and inefficient in utilizing laser light sources effectively.
Innovation Solution
A digital image projector system utilizing a light assembly with a temporally varying optical phase shifting device and a polarization maintaining optical integrator, combined with multiple laser arrays to achieve far-field illumination, reducing speckle through angular, spatial, and diffractive mixing, and maintaining inherent polarization states for improved etendue matching and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional light sources and optics are used in digital projection systems, then system complexity and cost are reduced, but brightness and image quality cannot match film projection
Solution Approach 1:
The patent replaces conventional mechanical projection systems with laser-based optical systems. Specifically, it uses laser light sources combined with spatial light modulators (SLMs) and specialized optics to achieve film-quality brightness and image formation, substituting traditional arc lamp-based projection mechanics with coherent laser illumination and digital micromirror or liquid crystal modulation
Solution Approach 2:
The patent changes key optical parameters by using laser light sources with specific coherence properties, wavelength stability, and spatial coherence. It employs SLMs that modulate light at the pixel level with high precision, and uses optical integrators that transform the laser beam parameters to achieve uniform illumination with high brightness comparable to film projection
2Illumination intensity
If laser light sources are used to achieve high brightness, then illumination intensity improves, but laser speckle and non-uniformity occur
Solution Approach 1:
The patent introduces an optical integrator as an intermediary component between the laser light source and the spatial light modulator. This optical integrator (such as a lenslet array or microlens array) acts as a mediator that spatially distributes and averages the laser light, eliminating speckle patterns while maintaining high brightness and uniform illumination across the projection area
Solution Approach 2:
The patent uses an optical integrator that transforms the one-dimensional laser beam into two-dimensional uniform illumination. The lenslet array divides the laser beam into multiple sub-beams that illuminate different regions of the SLM, effectively adding spatial dimensionality to distribute the coherent light and eliminate speckle while maintaining high brightness
3Quantity of substance
If high numerical aperture optics are used to increase etendue, then light throughput improves, but device complexity and cost increase
Solution Approach 1:
The patent employs dynamic control of the optical system through spatial light modulators that can rapidly switch between different optical paths and configurations. The SLMs dynamically modulate the phase and amplitude of light from different numerical aperture regions, allowing the system to adaptively optimize light throughput while managing complexity through software-controlled optical routing rather than fixed complex hardware
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 provides a high-quality, cost-effective, and efficient digital projection system with reduced laser speckle, optimized etendue, and enhanced brightness, capable of producing stereoscopic images with improved uniformity and brightness comparable to conventional cinema projection systems.
Implementation Method 1
a temporally varying optical phase shifting device configured to be in the light path
Implementation Method 2
an optical integrator configured to be in the far field portion of the light path
Implementation Method 3
projected light having an overlapping far field illumination in a far field illumination portion of the light path
Implementation Method 4
The LCD forms an image as an array of pixels by selectively modulating the polarization state of incident light for each corresponding pixel
Implementation Method 5
at least one laser array light source, the projected light having an overlapping far field illumination
Implementation Method 6
utilizing a light assembly with a temporally varying optical phase shifting device and a polarization maintaining optical integrator, combined with multiple laser arrays
Implementation Method 7
reducing speckle through angular, spatial, and diffractive mixing
Implementation Method 8
reducing speckle through angular, spatial, and diffractive mixing
Data Source
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AI summary
A digital image projector includes a light assembly configured to project light along a light path from at least one laser array light source, the projected light having an overlapping far field illumination in a far field illumination portion of the light path; a temporally varying optical phase shifting device configured to be in the light path; an optical integrator configured to be in the light path; a spatial light modulator located downstream of the temporally varying optical phase shifting device and the optical integrator in the light path, the spatial light modulator configured to be located in the far field illumination portion of the light path; and projection optics located downstream of the spatial light modulator in the light path, the projection optics configured to direct substantially speckle free light from the spatial light modulator toward a display surface.