Fixed-Focus Lens Aberration Control via Segmented Aspheric Groups
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Solution Overview
Problem
Existing small LED projectors face challenges in increasing brightness without increasing LED power, leading to image aberration issues in lenses with large apertures, which are costly and complex to manufacture.
Innovation Solution
A fixed-focus lens design comprising a first and second lens group with aspheric lenses, where the second lens group has a positive dioptre, allowing for a smaller f-number and reduced aberration, while maintaining a compact size and lower fabrication costs by focusing through the movement of both lens groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a lens with large aperture is adopted to increase brightness, then light utilization efficiency is improved, but image aberration increases
Solution Approach 1:
The lens is divided into multiple lens groups (first lens group with positive dioptre, second lens group with negative dioptre, third lens group with positive dioptre) where each group contains specific numbers of lenses (1-3 lenses per group). This segmentation allows each group to be optimized for specific aberration correction while maintaining the overall large aperture for brightness, resolving the contradiction between light utilization and image quality.
Solution Approach 2:
Different regions of the lens system are assigned different optical characteristics. The first, second, and third lens groups have different dioptre values and aberration correction functions tailored to their specific positions and roles. This local optimization allows the system to achieve both large aperture brightness and effective aberration correction without compromising either aspect.
2Object-affected harmful factors
If aspheric lenses are used to reduce image aberration, then optical quality is improved, but fabrication cost and device complexity increase
Solution Approach 1:
Instead of using multiple complex aspheric lenses, the patent segments the correction function across multiple lens groups with different dioptre values. Each group contains a small number of lenses (1-3) with specific optical characteristics, distributing the aberration correction workload and reducing the complexity of any single lens element while maintaining overall optical quality.
Solution Approach 2:
The patent achieves aberration correction by varying the dioptre values and optical characteristics across different lens groups rather than relying solely on complex aspheric surface geometries. This parameter-based approach simplifies individual lens fabrication while achieving the same optical effect, thereby reducing both complexity and cost.
3Object-affected harmful factors
If more lenses are added to reduce image aberration, then optical quality is improved, but device complexity and fabrication cost increase
Solution Approach 1:
The lens system is segmented into three functional groups with specific aberration correction roles. Each group contains a limited number of lenses (1-3 lenses per group), which optimizes the balance between aberration correction effectiveness and manufacturing complexity. This segmented approach avoids the need for excessive numbers of lenses while achieving adequate optical quality.
Solution Approach 2:
Instead of increasing the number of lenses, the patent achieves aberration reduction by optimizing the dioptre values and optical parameters of the existing lens groups. This parameter optimization approach achieves effective aberration correction with fewer lenses, thereby reducing fabrication cost and manufacturing complexity.
4Illumination intensity
If a lens with f-number between 1.74 and 2.16 is used to achieve large aperture, then brightness is improved, but fabrication cost greatly increases
Solution Approach 1:
The lens system achieves large aperture brightness through a segmented multi-group structure where each group contributes to both optical performance and cost control. The first, second, and third lens groups are designed with specific dioptre values and lens counts that balance brightness requirements with manufacturing feasibility, avoiding the excessive cost of traditional single-group high-aperture lenses.
Solution Approach 2:
The patent achieves adequate brightness with f-number between 1.74 and 2.16 by optimizing the cumulative optical power and aperture distribution across the three lens groups. This parameter optimization allows the system to achieve the desired brightness level while controlling fabrication cost through reasonable lens specifications and group configurations.
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 large aperture with reduced aberration, simplifying the structure and assembly, and lowering production costs, resulting in optimal imaging quality and improved brightness without the need for extensive lens groups or high-power LEDs.
Implementation Method 1
a lens with two aspheric lenses is disclosed in U.S. Pat. No. 5,920,433
Implementation Method 2
Image aberration has always been a major problem in the design of lenses with large apertures (for example, with their f-numbers smaller than 2). One technique for resolving this problem is to adopt aspheric lenses.
Implementation Method 3
the lens focuses by moving the second lens group
Data Source
AI summary
A fixed-focus lens disposed between an enlarged side and a reduced side is provided. An f-number of the fixed-focus lens is smaller than or equal to 2. The fixed-focus lens includes a first lens group and a second lens group. The first lens group includes a first lens, wherein the first lens is an aspheric lens. The second lens group, disposed between the first lens group and the reduced side, has a positive dioptre. The second lens group includes a second lens, wherein the second lens is an aspheric lens. The fixed-focus lens focuses by moving the first and the second lens group and satisfies 0.1<|f/f1|<1, 0.2<|f/f2|<1.5, and 1.5<L/BEL<3.5, where f, L, and BFL are respectively a focal length, a total length, and a back focal length of the fixed-focus lens, and f1 and f2 are respectively an effective focal length of the first and the second lens group.