Projector Optical Systems for Reducing Color Unevenness
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Solution Overview
Problem
The reduction in pixel pitch of projectors leads to light diffraction, causing unevenness in color projection due to the divergence of red, green, and blue light, particularly with digital micromirror devices (DMDs), resulting in reduced intensity and color unevenness in the projected image.
Innovation Solution
A projector configuration with a first optical system for red light and a second optical system for green and blue light, where the f-number of the first optical system is greater than the second, mitigates diffraction by preventing divergence of red light from the projection lens, maintaining overall brightness and reducing color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pixel pitch is reduced to increase resolution, then the image quality is improved, but light diffraction occurs causing color unevenness and luminous flux divergence
Solution Approach 1:
The patent applies parameter changes by adjusting the f-number specifically for the red light optical system to be larger than that of green and blue light systems. This parameter adjustment compensates for the greater diffraction effect on red light (longer wavelength) while maintaining proper illumination for green and blue light, thereby resolving the color unevenness caused by reduced pixel pitch
Solution Approach 2:
The patent implements local quality by applying different f-numbers to different wavelength channels (red vs. green/blue). The red light optical system uses a larger f-number tailored to its specific diffraction characteristics, while green and blue light systems use smaller f-numbers appropriate for their shorter wavelengths, ensuring each color channel is optimized for its diffraction properties
2Object-affected harmful factors
If the f-number of the first optical system is increased to mitigate red light diffraction, then color unevenness is reduced, but the overall light intensity may decrease
Solution Approach 1:
The patent applies local quality by optimizing the f-number for each wavelength channel independently. The red light system uses a larger f-number to address its specific diffraction problem, while green and blue light systems use smaller f-numbers to maintain their light intensity, achieving color uniformity without sacrificing overall brightness
Solution Approach 2:
The patent changes the f-number parameter differently for each optical system based on the wavelength-specific diffraction characteristics. By increasing only the red light system's f-number while keeping green and blue systems at lower f-numbers, the patent compensates for red light loss without reducing the intensity of other colors, thereby maintaining overall image brightness
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 color unevenness and maintains brightness by controlling the f-number of the optical systems for each wavelength, ensuring uniform color distribution on the projected image.
Implementation Method 1
the phenomenon of light diffraction occurs in image forming units. The diffraction phenomenon causes spreading of the luminous flux of red light, green light, and blue light that has passed through the image forming units
Implementation Method 2
The red light has a longer wavelength than green light and blue light, and the degree of diffraction is therefore greater
Data Source
AI summary
A projector includes: a light source that emits light of a first color and a second color; a first image formation element that forms a first image light of the first color; a second image formation element that forms a second image light of the second color; a projection lens that projects the first image light and the second image light to the outside; a first optical system that guides light of the first color that is emitted from the light source to the first image formation element, and guides light of the first color from the first image formation element to the projection lens; and a second optical system that guides light of the second color that is emitted from the light source to the second image formation element, and guides light of the second color from the second image formation element to the projection lens.