Fresnel Lens Group Beam Shape Control
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Solution Overview
Problem
Projectors using Fresnel lenses suffer from beam distribution issues due to varying transmittance with polarization direction and angle of incidence, leading to elliptical beam shapes and dark peripheral portions in projection images.
Innovation Solution
A projector design featuring a Fresnel lens group with a first Fresnel lens having a Fresnel surface on the incident side and a planar surface on the exiting side, and a second Fresnel lens with a planar incident surface and Fresnel surface on the exiting side, both with positive power, to minimize lens power and maintain a circular beam distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single Fresnel lens is used to parallelize the beam from the light source, then the beam can be parallelized, but the beam distribution becomes elliptical due to varying transmittance with polarization direction and angle of incidence, causing dark peripheral portions in the projection image
Solution Approach 1:
The single Fresnel lens is divided into multiple Fresnel lenses (first Fresnel lens and second Fresnel lens) arranged in sequence. Each lens has a specific focal length and is positioned at a determined distance from the light source. This segmentation allows each lens to contribute to parallelizing the beam with reduced polarization-dependent transmittance variation, maintaining circular beam distribution and eliminating dark peripheral portions.
2Speed
If the Fresnel lens has high positive power to effectively parallelize the beam, then the beam parallelization is improved, but the beam shape distortion increases and dark peripheral portions appear
Solution Approach 1:
The high positive power requirement is divided between multiple Fresnel lenses with lower individual powers. The first Fresnel lens has a first focal length and the second Fresnel lens has a second focal length, with each lens positioned at a specific distance from the light source. This distribution of optical power reduces the beam shape distortion and polarization-dependent transmittance variation that would occur with a single high-power lens, while still achieving effective beam parallelization.
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 the change in beam shape, suppressing dark peripheral portions and enabling uniform brightness in projected images by maintaining a nearly circular beam distribution.
Implementation Method 1
A projector that parallelizes the beam from a light source by using a Fresnel lens
Implementation Method 2
The Fresnel lens parallelizes the beam from the light source
Implementation Method 3
a light-incident-side polarizer that transmits the beam having exited out of the Fresnel lens
Implementation Method 4
a liquid crystal panel that modulates the beam having exited out of the light-incident-side polarizer to form a projection image
Data Source
AI summary
A projector includes a light source, a Fresnel lens group parallelizing the beam output from the light source, a light-incident-side polarizer transmitting the beam having exited out of the Fresnel lens group, a light modulator modulating the beam having passed through the light-incident-side polarizer to form a projection image, a light-exiting-side polarizer transmitting the beam modulated by the light modulator, and a projection lens projecting the beam having passed through the light-exiting-side polarizer. The Fresnel lens group includes a first Fresnel lens having positive power and disposed at a position closest to the light source in the Fresnel lens group, and a second Fresnel lens having positive power and disposed at a position shifted from the first Fresnel lens toward the light modulator. The light incident surface of the first Fresnel lens has a Fresnel surface. The light exiting surface of the first Fresnel lens has no Fresnel surface.