Projector Optical Systems for Color Uniformity
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Solution Overview
Problem
The reduction in pixel pitch of projector image forming units leads to light diffraction, causing unevenness in color projection due to the divergence of red, green, and blue light, particularly with DMDs, resulting in reduced intensity and color unevenness in the projected image.
Innovation Solution
A projector design incorporating a first optical system with a higher f-number for red light and a second optical system with a lower f-number for green and blue light, using a combination of optical components like TIR prisms and color prisms to separate and recombine light paths, ensuring uniform color distribution on the screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel pitch is reduced to improve resolution, then the image quality is improved, but light diffraction occurs causing color unevenness and reduced intensity
Solution Approach 1:
The patent applies different optical systems with different f-numbers for different wavelengths. Specifically, a first optical system with a larger f-number is used for red light, while a second optical system with a smaller f-number is used for green and blue light. This local differentiation of optical characteristics compensates for the wavelength-dependent diffraction effects, ensuring uniform light distribution across the projection lens pupil for all colors.
2Productivity
If DMDs are used with reduced micromirror pitch to improve pixel density, then the resolution is improved, but diffraction causes light divergence from the projection lens pupil
Solution Approach 1:
The patent changes the optical parameters (f-number) of the optical systems for different wavelengths. By using a first optical system with a larger f-number for red light and a second optical system with a smaller f-number for green and blue light, the patent adjusts the light convergence characteristics to compensate for diffraction effects, ensuring that all wavelengths focus properly within the projection lens pupil.
3Illumination intensity
If the f-number of the optical system is increased to reduce diffraction, then the light convergence is improved, but the overall light intensity and brightness are reduced
Solution Approach 1:
The patent applies different f-numbers to different optical systems based on the wavelength. The first optical system for red light uses a larger f-number to improve convergence, while the second optical system for green and blue light uses a smaller f-number to maintain brightness. This localized optimization ensures that each wavelength achieves appropriate convergence without unnecessary loss of overall light intensity.
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 configuration reduces color unevenness and maintains overall brightness by minimizing divergence of red light from the projection lens, resulting in a more uniform and even projection of synthesized red, green, and blue light.
Implementation Method 1
The first optical system guides light of a first wavelength that is emitted from the light source to the projection lens
Implementation Method 2
The second optical system guides light of a second wavelength that is emitted from the light source to the projection lens
Implementation Method 3
The image forming units adjust the intensity of light emitted from the light source for each pixel and form image light
Implementation Method 4
The projection lens projects image light that was formed in the image forming units to the outside
Data Source
AI summary
A projector has a light source, image forming units, a projection lens, a first optical system and a second optical system. The image forming units form image light by adjusting, on a per-pixel basis, the intensity of light emitted by the light source. The projection lens projects the image light formed by the image forming units to the outside. The first optical system guides light of a first wavelength emitted by the light source to the projection lens, and the second optical system guides light of a second wavelength emitted by the light source to the projection lens. The f-number of the first optical system is higher than the f-number of the second optical system.