Imaging Lens for Projection Displays with Segmented Optical Systems
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Solution Overview
Problem
Existing imaging lenses for projection-type display apparatuses have insufficient angle of view and aberration fluctuation, and high F-Number, which limits their ability to project high-quality images onto large screens from short distances.
Innovation Solution
An imaging lens design comprising a first imaging optical system that forms an intermediate image and a second system that re-forms it, with specific configurations of negative and positive lenses, including a focus lens group that moves along the optical axis for focusing, and cemented lenses to control aberrations and maintain a wide angle with a small F-Number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a long back focus is used to dispose color synthesis prism and avoid thermal problems, then thermal stability is improved, but the angle of view becomes narrow and the F-Number increases
Solution Approach 1:
The imaging lens is divided into two separate imaging optical systems (first imaging optical system G1 and second imaging optical system G2) that form and re-form an intermediate image. This segmentation allows each system to be optimized independently, enabling a wide angle of view while maintaining a long back focus for thermal stability and prism accommodation.
Solution Approach 2:
An intermediate image is introduced as a mediator between the object and final image planes. The first imaging optical system forms an intermediate image at a position conjugate to a magnified-side imaging surface, and the second imaging optical system re-forms this intermediate image on a reduced-side imaging surface. This intermediary approach enables better aberration control and allows the back focus to be extended for thermal management while maintaining wide-angle performance.
2Reliability
If telecentricity on the reduced side is increased to satisfy color synthesis prism requirements, then spectral characteristic stability is improved, but the F-Number increases and aberration correction becomes more difficult
Solution Approach 1:
The first imaging optical system is designed with dynamic aberration control capabilities through its specific lens configuration (including at least four consecutive negative lenses and a sub-lens group with positive-negative-positive arrangement). This dynamic design allows the system to maintain telecentricity on the reduced side for spectral stability while actively correcting aberrations across the wide field of view through careful lens positioning and curvature design.
3Adaptability or versatility
If zooming function and wide angle of view are increased to project onto large screens from short distance, then projection versatility is improved, but aberration fluctuation with distance changes increases
Solution Approach 1:
The patent performs preliminary aberration correction by carefully designing the lens configurations and positions in the first imaging optical system before actual projection occurs. The specific arrangement of negative and positive lenses, along with the intermediate image formation, pre-compensates for aberrations that would otherwise fluctuate with projection distance changes, ensuring consistent image quality across different projection scenarios.
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 design achieves a wide angle of view, reduced aberration fluctuation, and a small F-Number, enhancing the projection quality and adaptability for large-screen displays from short distances.
Implementation Method 1
a first imaging optical system that forms an intermediate image at a position conjugate to a magnified-side imaging surface
Implementation Method 2
a second imaging optical system that re-forms the intermediate image on a reduced-side imaging surface
Implementation Method 3
a focus lens group adjacent to a reduced side of the first sub-lens group, in order from a position closest to the magnified side, and only the focus lens group moves along an optical axis during focusing
Data Source
AI summary
The imaging lens consists of a first imaging optical system that forms an intermediate image at a position conjugate to a magnified-side imaging surface and a second imaging optical system that re-forms the intermediate image on a reduced-side imaging surface, in order from a magnified side. The first imaging optical system includes at least four consecutive negative lenses, a first sub-lens group consisting of a positive lens, a negative lens, and a positive lens in order from the magnified side, and a focus lens group adjacent to a reduced side of the first sub-lens group, in order from a position closest to the magnified side, and only the focus lens group moves along an optical axis during focusing.