Compact Three-Lens Imaging System for Aberration Correction
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Solution Overview
Problem
Conventional imaging lens systems for portable devices face challenges in achieving high resolution, low cost, and compact size due to limitations in correcting spherical and astigmatic aberrations, especially at small F numbers and large wide angles, and are often heavy and expensive.
Innovation Solution
A compact imaging lens system comprising three aspheric plastic lens elements, including a positive meniscus lens for focusing power and aberration balance, a negative lens for chromatic and off-axis aberration correction, and a third negative lens for off-axis aberration correction, with specific optical design parameters to ensure low tolerance sensitivity and short length, satisfying conditions like 0.2<fl/F<1.2 and |R5−R4|/F<0.3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spherical glass lenses are used, then material availability and color aberration correction are improved, but spherical aberration and astigmatic aberration correction become difficult, and device dimensions and cost increase
Solution Approach 1:
The patent employs aspheric surfaces on lens elements instead of traditional spherical surfaces. The aspheric shapes allow for better correction of spherical aberration and astigmatic aberration while maintaining compact dimensions. Specifically, the objective lens includes multiple lens elements with aspheric surfaces that progressively correct off-axis aberrations.
Solution Approach 2:
The patent uses a hybrid lens system combining plastic and glass materials. The objective lens comprises plastic lens elements for the front groups and a glass lens element for the rear group. This composite approach allows optimization of each material's properties: plastic for aberration correction and compactness, glass for color aberration correction and durability.
2Measurement precision
If more lens elements are added to improve resolution, then optical performance is improved, but cost and weight increase
Solution Approach 1:
The patent optimizes specific parameter ranges to achieve high resolution with minimal lens elements. Key parameters include the focal length ratio (0.3 < fl/F < 1.2), the third lens element's focus gradient (0.2 < |d3| < 0.5), and curvature ratios (0.1 < |R5-R4|/F < 0.4). These parameter optimizations allow effective aberration correction and high resolution with only three lens elements.
Solution Approach 2:
The patent applies different material properties and surface characteristics to different regions of the lens system. The third lens element has a focus that varies from negative in the near-axis area to positive at the edge portion, providing localized aberration correction. The aspheric surfaces are strategically positioned to correct specific aberration types in different field regions.
3Length of moving object
If lens system is compacted to reduce dimensions, then portability is improved, but aberration correction capability deteriorates
Solution Approach 1:
The patent uses aspheric surfaces on multiple lens elements to achieve effective aberration correction in a compact configuration. The aspheric shapes enable better control of light rays at various angles without requiring additional lens elements that would increase length. The objective lens has a total length TT satisfying 0.4 < TT/fl < 0.8, achieving compactness while maintaining correction capability.
Solution Approach 2:
The patent introduces an aperture stop as an intermediary element between the first and second lens elements. This aperture stop helps control the cone of light entering subsequent lens elements, reducing the need for complex aberration correction in later elements and enabling a more compact overall design.
4Ease of manufacture
If plastic lenses are used instead of glass lenses, then cost and weight are reduced, but transparent capability deteriorates
Solution Approach 1:
The patent employs a hybrid lens system where plastic lens elements (first and second lens elements) are combined with a glass lens element (third lens element). This composite approach leverages the advantages of both materials: plastic provides cost-effectiveness, ease of aspheric shaping, and weight reduction, while glass provides superior transparency and color aberration correction capability.
Solution Approach 2:
The patent optimizes the refractive indices and Abbe numbers of the plastic and glass materials used. The plastic lens elements use materials with refractive indices nd1 and nd2, while the glass lens element has refractive index nd3. These parameter selections balance transparency, aberration correction, and cost considerations.
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 system achieves high optical performance, low manufacturing sensitivity, and reduced cost and weight, while maintaining a high resolution and wide angle of field, making it suitable for high-resolution portable devices.
Implementation Method 1
a first positive lens element, an aperture, a second negative lens element, and a third negative lens element. The first, second, and third lens elements are aspheric lenses each having at least one aspheric surface.
Data Source
AI summary
A compact imaging lens system includes three lenses. The first lens is a positive meniscus lens having a convex side facing toward the image side, which has a big focusing power and is provided to capture image and for balance of aberration. The first lens serves to make the lens system a low sensitivity lens system. The second lens is a negative lens and is provided mainly for correcting chromatic aberration and off-axis aberration. An aperture is set between the first and second lenses, and this is of benefit to balance of aberration. The third lens is a negative lens and is provided for correcting off axis aberration. All the lenses can be made of plastics. This facilitates cost reduction, weight reduction, while still maintains a high resolution.