Compact Imaging Lens with Cemented Groups for Aberration Correction
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Solution Overview
Problem
There is a demand for an imaging lens that can be made smaller while maintaining a small F number and excellent performance, as existing lenses face challenges in achieving both compact size and high optical quality.
Innovation Solution
The imaging lens is configured with a front group comprising a meniscus lens, a first cemented lens with negative refractive power, and a second cemented lens with positive refractive power, along with a rear group featuring a negative refractive power lens closest to the image side, satisfying specific conditional expressions to optimize focal lengths, surface curvatures, and refractive indices for aberration correction and downsizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lens size is reduced to make the imaging lens more compact, then the F number increases and optical performance deteriorates
Solution Approach 1:
The imaging lens is divided into a front group and a rear group with specific lens arrangements. The front group includes a meniscus lens and two cemented lenses, while the rear group includes specific positive and negative lenses. This segmentation allows each group to contribute differently to the overall optical performance, enabling compact size while maintaining small F number through optimized light path management in each segment.
Solution Approach 2:
Different regions of the lens system have specialized functions optimized for their local requirements. The front group focuses on initial light gathering and aberration control, while the rear group optimizes for image plane formation. Specific lenses within each group have tailored curvatures and refractive powers to address local optical challenges, enabling the entire system to achieve small F number in a compact form.
2Volume of moving object
If the lens size is reduced to make the imaging lens more compact, then aberration correction becomes more difficult
Solution Approach 1:
The imaging lens employs cemented lenses that combine multiple lens materials with different refractive indices and Abbe numbers. The first cemented lens combines a positive lens and negative lens, while the second cemented lens combines another positive and negative lens pair. These composite structures enable simultaneous correction of spherical aberration, coma, and chromatic aberration within the compact lens groups, as each material contributes differently to the overall aberration profile.
Solution Approach 2:
The patent specifies precise parameter ranges for each lens element to optimize aberration correction in the compact configuration. Conditional expressions define relationships between focal lengths, radii of curvature, and refractive indices. By carefully controlling these parameters within specified ranges, the design achieves excellent aberration correction despite the reduced overall size, allowing each lens element to contribute optimally to the correction of various aberration types.
3Illumination intensity
If the F number is reduced to improve light gathering ability, then the lens diameter increases
Solution Approach 1:
The lens design incorporates aspherical surfaces on key lens elements, including the meniscus lens and several lenses in the rear group. These aspherical surfaces dynamically adjust the refraction of light rays across different zones of the lens, enabling efficient light gathering at small F number without requiring proportionally larger lens diameters. The aspherical profiles optimize the light path to reduce vignetting and improve illumination uniformity while maintaining compact dimensions.
Solution Approach 2:
The patent replaces traditional spherical lens surfaces with aspherical surfaces to achieve better light control. This substitution allows the lens system to achieve small F number with smaller diameter by using the geometric properties of aspherical surfaces to more efficiently direct light rays to the image plane, reducing the need for larger aperture sizes that would be required with conventional spherical surfaces.
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 allows for a compact imaging lens with a small F number and excellent optical performance, effectively correcting spherical aberrations and chromatic aberrations while ensuring appropriate back focal length and reducing lens diameter, suitable for use in imaging apparatuses like night vision systems.
Implementation Method 1
a meniscus lens having a positive refractive power and having a convex object side surface
Implementation Method 2
a first cemented lens having a convex surface closest to the object side and a concave surface closest to the image side, constituted by cementing a positive lens and a negative lens
Implementation Method 3
having a negative refractive power as a whole, and a second cemented lens having a positive refractive power as a whole
Implementation Method 4
a most image side lens which has a negative refractive power at a position closest to the image side and has a concave object side surface
Data Source
AI summary
An imaging lens consists of a front group and a rear group in order from the object side to the image side. The front group includes, as lenses, in order from the object side to the image side, only a positive meniscus lens having a surface convex toward the object side, a first cemented lens having a negative power as a whole, and a second cemented lens having a positive power as a whole. In the first cemented lens, a positive lens and a negative lens are cemented in order from the object side, with a surface convex toward the object side and a surface concave toward the image side. The rear group includes a negative most image side lens having a surface concave toward the object side at a position closest to the image side.