Variable Magnification Optical System Aberration Correction
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Solution Overview
Problem
Existing variable magnification optical systems for projection have narrow full angles of view, making it difficult to maintain excellent projection performance while correcting various aberrations such as distortion, astigmatism, and curvature of field, especially when increasing the angle of view beyond 55 degrees.
Innovation Solution
A variable magnification optical system consisting of a negative lens group with an aspheric surface and a positive lens group, where the distance between these groups changes during magnification, allowing for a wide angle of view while effectively correcting aberrations, using a retro-focus type structure with six lenses, including a plastic aspheric first lens and a biconcave second lens, to maintain a simple and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the angle of view is increased beyond 55 degrees while maintaining a simple lens structure, then the coverage area is improved, but aberration correction becomes difficult and projection performance deteriorates
Solution Approach 1:
The lens system is divided into multiple lens groups (first lens group with negative refractive power, second lens group with positive refractive power, third lens group with negative refractive power) that can move independently along the optical axis. This segmentation allows each group to be optimized for specific aberration correction while collectively achieving wide angle of view, resolving the contradiction between coverage area and aberration correction.
Solution Approach 2:
The patent employs a variable magnification optical system where lens groups can dynamically adjust their positions along the optical axis during magnification changes. This dynamic configuration enables the system to maintain optimal aberration correction across different focal lengths while providing wide angle of view, allowing the system to adapt to different projection requirements.
2Device complexity
If a simple lens structure with few lenses is used, then device complexity and cost are reduced, but the ability to correct various aberrations deteriorates
Solution Approach 1:
The lens system is divided into three lens groups with specific refractive power distributions. This segmentation allows the system to correct multiple aberrations (distortion, astigmatism, curvature of field) more effectively than a simple single-group structure, while maintaining relatively low complexity through modular design where each group has a clear functional assignment.
Solution Approach 2:
The patent utilizes lenses with different refractive indices and aberration characteristics combined in a multi-group structure. By selecting appropriate glass types and configurations for each lens group, the system achieves superior aberration correction without requiring excessive numbers of lenses, balancing performance with structural simplicity.
3Device complexity
If the number of lenses is reduced to five, then device complexity is lowered, but the full angle of view becomes narrow (less than or equal to 55 degrees)
Solution Approach 1:
The lens system is divided into three lens groups that can be configured to provide wide angle of view. By strategically arranging groups with negative and positive refractive powers, the system achieves a full angle of view of 60 degrees or more while maintaining a manageable number of lenses, resolving the contradiction between component count and field coverage.
Solution Approach 2:
The patent utilizes the optical path dimension by arranging lens groups at different positions along the optical axis with variable spacing. This spatial arrangement in the optical dimension allows the system to achieve wide angle of view and variable magnification ratios without increasing the lateral footprint or number of lenses excessively.
4Manufacturing precision
If a retro-focus type structure with aspheric surfaces is used, then aberration correction is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies aspheric surfaces selectively to specific lens elements (first lens and second lens) where they provide the most significant aberration correction benefit, rather than making all lenses aspheric. This localized application of complex surface geometry achieves improved projection performance while minimizing the overall manufacturing complexity and cost impact.
Solution Approach 2:
The lens system is segmented into groups where aspheric surfaces are applied to specific constituent lenses that require them for optimal performance. By dividing the system this way, the patent can incorporate sophisticated surface geometries only where necessary, maintaining ease of manufacture for the overall system while achieving superior aberration correction at critical points.
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 provides a low-priced, small-sized optical system with a wide angle of view and excellent aberration correction, achieving sharp and precise images while maintaining a simple lens structure, suitable for projection-type display apparatuses.
Implementation Method 1
a first lens including an aspheric surface and a second lens that is a single lens having negative refractive power
Implementation Method 2
a distance on an optical axis between the negative lens group and the positive lens group changes during magnification change
Data Source
AI summary
A variable magnification optical system for projection consists of a negative lens group and a positive lens group in this order from a magnification side. A distance on an optical axis between the negative lens group and the positive lens group changes during magnification change, and an entire system substantially consists of six lenses. The negative lens group consists of a first lens including an aspheric surface and a second lens that is a negative single lens in this order from the magnification side.