Imaging Lens Aberration Correction via Cemented Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current imaging lenses for surveillance and on-board cameras face challenges in achieving a small F number and compact size while maintaining good optical performance, with existing lenses either having a large F number or being too long, making them unsuitable for video capture at night and not adequately downsized for modern applications.
Innovation Solution
The proposed imaging lens configuration includes a negative first lens, a positive meniscus second lens, a stop, a positive third lens, and a cemented lens, with specific refractive power and positional adjustments to satisfy conditional expressions that ensure a small F number, downsizing, and correction of spherical and chromatic aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional imaging lens configuration is used, then the lens can be manufactured with standard design, but the F number is large and the lens size is excessive
Solution Approach 1:
The lens is divided into five distinct lens elements (first through fifth lenses) with specific refractive powers and configurations. Each lens element serves a specific function in correcting aberrations and achieving the desired optical performance, allowing the system to achieve a small F number while maintaining manufacturability through standardized design of individual elements.
Solution Approach 2:
The patent applies specific parameter constraints to achieve the desired optical performance: the Abbe number of the second lens is constrained to ν2 > 30, the focal length ratio is constrained to 2.5 < L/f < 4.0, and the back focus ratio is constrained to 0.5 < Bf/f < 1.3. These parameter changes enable the lens to achieve a small F number while maintaining standard manufacturing capabilities.
2Length of moving object
If the lens is downsized to meet compact requirements, then the lens length is reduced, but optical performance deteriorates due to insufficient aberration correction
Solution Approach 1:
Different lens elements are assigned specific local functions to correct different types of aberrations. The positive meniscus second lens specifically corrects spherical aberration, the cemented lens (fourth and fifth lenses) corrects chromatic aberration, and each element's curvature and refractive index are optimized for its local position in the optical system. This localized optimization enables compact design while maintaining high optical performance.
Solution Approach 2:
The patent uses a cemented lens composed of two different lens materials (fourth lens and fifth lens) with different Abbe numbers. This composite structure enables simultaneous correction of chromatic aberration while maintaining a compact overall lens length, as the different materials compensate for each other's optical deficiencies.
3Illumination intensity
If a bright lens with small F number is designed, then nighttime video capture is enabled, but spherical and chromatic aberrations become difficult to correct
Solution Approach 1:
The patent employs a dynamic balance of refractive powers across the five lens elements. The positive meniscus second lens provides strong spherical aberration correction capability, while the cemented lens (fourth and fifth lenses) provides chromatic aberration correction. The stop position is strategically placed to control the balance between spherical and chromatic aberrations, enabling the system to achieve small F number (high brightness) while maintaining precise aberration correction.
Solution Approach 2:
The stop (aperture diaphragm) acts as an intermediary element that controls the balance between spherical and chromatic aberrations. By strategically positioning the stop between the second and third lenses, the system can manage the trade-off between achieving a small F number for brightness and maintaining precise aberration correction, as the stop limits the aperture angle to reduce spherical aberration while allowing the cemented lens to correct chromatic effects.
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 high-speed optical system with a small F number, effective aberration correction, and downsizing, making it suitable for use in surveillance and on-board cameras, particularly for nighttime video capture and wide temperature ranges.
Implementation Method 1
it is also possible to satisfactorily correct spherical aberration by forming the second lens as a positive meniscus lens convex toward the object side
Implementation Method 2
by satisfying the conditional expression (1), it is possible to satisfactorily correct longitudinal chromatic aberration
Data Source
AI summary
An imaging lens comprises, in order from an object side: a first lens that has a negative refractive power and is convex toward the object side; a second lens that has a positive refractive power and is a meniscus lens convex toward the object side; a stop; a third lens that has a positive refractive power and is convex toward an image side; and a cemented lens that has a positive refractive power as a whole and is formed by cementing a fourth lens and a fifth lens, wherein assuming that an Abbe number of the second lens with respect to d-line is ν2, a distance on an optical axis from a vertex of a surface of the first lens facing toward the object side to an image plane of the imaging lens is L, a focal length of the imaging lens is f, and a back focus of the imaging lens is Bf, the following conditional expressions (1) to (3) are satisfied:ν2>30 (1),2.5<L/f<4.0 (2), and0.5<Bf/f<1.3 (3).