White Light Projection System with Spatial Fourier Filtering
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Solution Overview
Problem
Conventional digital projectors, especially those compliant with the Digital Cinema Initiatives (DCI) specification, often have low contrast ratios, resulting in dark or black image regions appearing brighter than intended due to diffraction by digital micromirror devices (DMDs), which affects the overall image quality and accuracy in reproducing scenes for various viewers with different adaptation states.
Innovation Solution
A projection system utilizing a single illumination assembly that delivers white light, which is split into separate color channels by a white light prism and modulated independently before being recombined and filtered using an optical filter configured for spatial Fourier transformation, enhancing contrast by selectively blocking undesired diffraction orders and improving the dynamic range and resolution of projected images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional digital projector uses a three-channel prism assembly with a common light path, then the device complexity is reduced, but the contrast ratio deteriorates to 2,000:1 or less
Solution Approach 1:
The patent divides the common light path into separate illumination paths for each color channel (red, green, blue). Each channel has its own illumination assembly and prism path, allowing independent control and optimization of each channel's light path. This segmentation enables the system to achieve high contrast ratios (70K:1) by preventing cross-channel interference and allowing separate modulation of each color channel.
Solution Approach 2:
The patent introduces independent illumination angle adjustment for each color channel, adding a dimensional degree of freedom to the system. By controlling the illumination angle separately for each channel, the system can optimize light path separation and reduce unwanted diffraction effects, thereby improving contrast ratio while maintaining manageable device complexity.
2Measurement precision
If independent illumination angle adjustment is provided for each color channel, then the contrast ratio is improved to 70K:1, but the device complexity increases
Solution Approach 1:
The patent uses a single modulator that can be sequentially illuminated by different color channels through the separate prism paths. This universal modulator approach allows one component to serve multiple functions (modulating red, green, and blue light), reducing the need for multiple identical assemblies and thereby limiting the increase in device complexity while maintaining high contrast performance.
Solution Approach 2:
The system employs time-sequential illumination where each color channel is activated in periodic succession rather than simultaneously. The illumination assembly switches between channels in a periodic manner, allowing the single modulator to process each channel sequentially. This temporal multiplexing achieves high contrast ratios without requiring fully parallel independent paths for all channels, thus controlling device complexity.
3Adaptability or versatility
If dark regions are projected with high luminance to ensure visibility, then the image can be viewed by audiences with different adaptation states, but the contrast ratio deteriorates and dark regions appear brighter than intended
Solution Approach 1:
The patent replaces the mechanical/optical limitation of fixed luminance output with a controllable modulation system. By using independently adjustable illumination angles and sequential channel activation, the system can dynamically control the luminance of dark regions to be near-zero when needed, while still providing sufficient brightness for viewers with different adaptation states through the overall high-contrast capability of 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 significantly increases the contrast ratio, allowing for more accurate reproduction of images with higher dynamic range and resolution, effectively addressing the limitations of existing projector technologies by optimizing the illumination and filtering processes.
Implementation Method 1
A projection system utilizing a single illumination assembly that delivers white light, which is split into separate color channels by a white light prism
Implementation Method 2
enhancing contrast by selectively blocking undesired diffraction orders
Implementation Method 3
filtered using an optical filter configured for spatial Fourier transformation
Data Source
AI summary
Light projection systems using white light illumination. One embodiment provides a projection system using white light illumination. The projection system includes an illumination assembly configured to receive a white light input. A prism is configured to separate the white light input into color light inputs, redirect the color light inputs to respective modulators, and combine modulated color light inputs from the respective modulators into a white light output. An optical filter is configured to spatially Fourier transform the white light output to generate a filtered white light output. A projection lens assembly is configured to project the filtered white light output.