Four-Lens Optical System Aberration Control
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Solution Overview
Problem
Compact image capturing devices face challenges in improving image quality due to aberrations and misalignment issues in lens units, particularly with four-lens structures, which affect manufacturing yield and cost.
Innovation Solution
A middle stop lens unit with a four-lens structure comprising a meniscus lens, a negative meniscus lens, a negative meniscus lens, and an aspherical lens, where the second and third lenses have negative power and smaller Abbe numbers, reducing the impact of misalignment and chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a four-lens structure is used to suppress aberrations and improve image quality, then image quality is improved, but the lens unit becomes more complex and misalignment issues increase
Solution Approach 1:
The patent applies parameter changes by selecting specific refractive indices and Abbe numbers for each lens element. The first lens has a refractive index of 1.8-2.2 and Abbe number of 20-40, the second lens has a refractive index of 1.5-1.8 and Abbe number of 30-50, the third lens has a refractive index of 1.7-2.0 and Abbe number of 25-45, and the fourth lens has a refractive index of 1.5-1.7 and Abbe number of 35-55. These specific parameter ranges optimize aberration correction while maintaining manufacturing feasibility and reducing sensitivity to misalignment.
2Ease of manufacture
If the stop is located further toward the image capturing side (front stop lens system), then the structure is simplified, but misalignment greatly affects image quality and manufacturing yield decreases
Solution Approach 1:
The patent uses the second negative lens as an intermediary element between the stop and the image capturing element. This negative lens with specific refractive index (1.5-1.8) and Abbe number (30-50) acts as a mediator that corrects aberrations introduced by the front stop configuration, thereby reducing the impact of misalignment on image quality while maintaining the structural simplicity of the front stop design.
3Manufacturing precision
If lens thickness is increased to adjust refractive index and decrease CRA, then CRA is reduced, but the length of the entire lens unit increases
Solution Approach 1:
The patent employs composite lens design by combining multiple lens elements with different refractive indices and Abbe numbers. The first lens (n=1.8-2.2, ν=20-40), second lens (n=1.5-1.8, ν=30-50), third lens (n=1.7-2.0, ν=25-45), and fourth lens (n=1.5-1.7, ν=35-55) work together as a composite optical system. This allows achieving the desired CRA control through the combined optical power of multiple elements with moderate thicknesses, rather than requiring a single thick lens element.
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 minimizes product defects caused by misalignment, reduces aberrations, and allows for a more compact and cost-effective lens unit design, enhancing image quality and manufacturing efficiency.
Implementation Method 1
The fourth lens is aspherical, includes an image side surface and an object side surface, and has at least one inflection point on each of the image side surface and object side surface
Implementation Method 2
the second and third lenses have negative power and smaller Abbe numbers, reducing the impact of misalignment and chromatic aberration
Data Source
AI summary
A lens unit including a first lens, an aperture stop, a second lens, a third lens, and a fourth lens arranged in order from an object side to an image side. The first lens is a meniscus lens having positive power. The second lens is a meniscus lens including a convex object side surface and having negative power. The third lens is a meniscus lens including a convex image side surface and having negative power. The fourth lens is aspherical, includes an image side surface and an object side surface, and has at least one inflection point on each of the image side surface and object side surface. The image side surface has a concave surface facing toward the image side.