Retrofocus Imaging Optical System Aberration Control
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Solution Overview
Problem
Existing imaging optical systems struggle to achieve a balance between compactness, wide angle of view, and high performance while maintaining low aberrations and chromatic correction, particularly in retrofocus configurations with a limited number of lenses.
Innovation Solution
A retrofocus imaging optical system is designed with a specific arrangement of lenses, including a first lens with negative refractive power, a second lens with positive refractive index and convex object side surface, a third lens with negative refractive power and concave object side surface, and a fourth lens with positive refractive power and convex image side surface, along with optional additional lenses, satisfying specific refractive index and Abbe number conditions for the second lens material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a retrofocus configuration with a limited number of lenses is used, then the device complexity is reduced, but the manufacturing precision and aberration correction performance deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully selecting the refractive index and Abbe number of the lens materials to satisfy specific conditional expressions. The second lens uses material with refractive index nd between 1.94 and 2.20 and Abbe number νd between 15.0 and 20.0, which optimizes chromatic aberration correction. This material parameter selection enables high-performance aberration correction in a compact 5-6 lens retrofocus system, resolving the contradiction between reduced device complexity and maintained manufacturing precision.
2Device complexity
If the number of lens elements is reduced to 5 or 6, then the device complexity is reduced, but the imaging performance and chromatic correction worsen
Solution Approach 1:
The patent changes material parameters by specifying that the second lens must have refractive index nd between 1.94 and 2.20 and Abbe number νd between 15.0 and 20.0. This high refractive index material enables effective chromatic aberration correction with fewer lens elements. The specific parameter ranges allow the 5-6 lens retrofocus system to achieve reliable imaging performance that would otherwise require more complex multi-element designs.
Solution Approach 2:
The patent employs composite material strategy by combining lenses with different refractive indices and Abbe numbers. The second lens uses high refractive index material (nd=1.94-2.20) while other lenses use materials with different optical properties. This composite approach enables effective chromatic aberration correction across the visible spectrum using only 5-6 lens elements, maintaining reliable imaging performance while reducing device complexity.
3Adaptability or versatility
If a retrofocus configuration is used to achieve wide angle of view, then the field of view is improved, but the aberration control and chromatic correction worsen
Solution Approach 1:
The patent controls aberrations in the wide-angle retrofocus design by changing material parameters. The second lens uses high refractive index material (nd=1.94-2.20) with specific Abbe number (νd=15.0-20.0), which provides strong dispersion control. This parameter selection enables effective correction of chromatic and monochromatic aberrations across the wide field of view, resolving the contradiction between wide angle capability and aberration control.
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 enables a compact, wide-angle, high-performance imaging optical system with reduced aberrations and improved chromatic correction, suitable for use in camera apparatuses, achieving a wide half-angle view and large aperture with an F-number of about 1.6.
Implementation Method 1
The second lens L2 having a convex object side surface and having a positive refractive index... satisfying conditional expressions: 1.94≤nd≤2.20 and 15.0≤νd≤20.0, where nd represents a refractive index of a lens material of the second lens L2 at d-line, and νd represents an Abbe number of the lens material of the second lens L2 at d-line
Data Source
AI summary
An imaging optical system includes a first lens having a concave image side surface and a negative refractive power; a second lens having a convex object side surface and a positive refractive index; a third lens having a concave object side surface and a negative refractive power; a fourth lens having a convex image side surface and a positive refractive power; and a fifth lens having a convex object side surface and a positive refractive power in the order from the object side to the image side, optionally includes a lens on the image side of the fifth lens. The imaging optical system satisfies conditional expressions [1] 1.94<n2<2.20 and [2] 15.0<ν2<20.0, where ν2 and n2 represents an Abbe number and a refractive index of a lens material of the second lens L2 at d-line, respectively.