Color Dependent Aperture Stop for DMD Projectors
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Solution Overview
Problem
Current projector technologies face efficiency losses due to diffraction effects when using narrow band light sources, particularly with DMD devices, as the finer pitch of newer chips like the DC4K chip leads to unacceptable efficiency losses, and existing solutions fail to balance red transmission with maintaining contrast for blue and green light.
Innovation Solution
A color-dependent aperture (CDA) system is implemented in the projection lens, where the aperture stop size and shape vary by wavelength to match the angular distribution of light, optimizing the working f-number for each color band, thereby enhancing light transmission while maintaining contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single aperture stop size is used for all color bands, then the device complexity is reduced, but the light transmission efficiency for different colors cannot be optimized simultaneously
Solution Approach 1:
The aperture stop is designed with different transmission characteristics for different color bands. Specifically, the aperture allows red light to pass through with a larger effective opening while restricting blue and green light to a smaller opening, optimizing transmission efficiency for each color band according to its diffraction characteristics
Solution Approach 2:
The aperture stop parameters (size and shape) are varied as a function of wavelength. The aperture dimensions are specifically tailored for different color bands, with the red channel receiving a larger aperture opening compared to the blue and green channels, thereby optimizing light transmission for each wavelength range
2Productivity
If the aperture stop size is increased to improve red light transmission, then red light efficiency is improved, but contrast ratio for blue and green light deteriorates
Solution Approach 1:
The aperture stop provides different local openings for different color bands. The red light path receives a larger aperture opening to improve transmission, while the blue and green light paths receive a smaller effective opening to maintain contrast ratio, with each color band experiencing optimized local aperture characteristics
Solution Approach 2:
The aperture stop is designed with color-dependent transmission characteristics. By utilizing the different wavelengths of red, green, and blue light, the aperture creates color-specific opening sizes that optimize transmission for red while maintaining contrast for blue and green channels
3Reliability
If the aperture stop size is decreased to maintain contrast for blue and green light, then contrast ratio is maintained, but red light transmission efficiency deteriorates
Solution Approach 1:
Rather than using a uniformly small aperture, the system implements a color-dependent aperture that provides locally optimized openings: a larger effective aperture for red light to maintain transmission efficiency, and a smaller effective aperture for blue and green light to preserve contrast ratio
4Productivity
If a color-dependent aperture system is implemented, then light transmission efficiency for each color band is optimized, but the device complexity increases
Solution Approach 1:
The aperture stop parameters are designed to vary as a function of wavelength, creating color-dependent opening sizes. This is achieved through optical filtering and geometric arrangements that naturally produce different effective apertures for different color bands without requiring mechanically complex adjustable mechanisms
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 CDA system improves light transmission for red light without compromising contrast for blue and green light, optimizing the efficiency and contrast ratio in projection systems, particularly with DMD devices, by tailoring the aperture to the specific diffraction patterns of each color band.
Implementation Method 1
unacceptable efficiency losses were observed with various combinations of laser wavelengths and 4K DMD devices. These losses may be due to increased diffraction from the finer pitch of the DC4K chip
Data Source
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AI summary
Optical systems are provided that include illumination sources, micro-mirror array optical modulators, and an optical element. The micro-mirror array optical modulators can selectively modulate light beams, redirect light by diffraction and reflection, and provide an output modulated light beam that exhibits a diffraction handedness dependent on the spectral bandwidth of the light incident thereupon. The optical element has a color dependent aperture that defines portions of output modulated light beams that are transmitted and remaining portions that are blocked. An efficiency and contrast of each the output modulated light beams acquired by the optical element can be independently determined by a narrow spectral bandwidth of each of the light beams, the spectral characteristics of the color dependent aperture, and the diffraction handedness of the micro-mirror array optical modulators for the associated spectral bandwidth.