Five-Lens Imaging System with Composite Glass-Plastic Elements
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Solution Overview
Problem
Existing imaging lenses for in-vehicle and surveillance cameras face challenges in achieving a balance of small size, low cost, high telecentricity, long back focus, and small F-number while maintaining high optical performance and weather resistance.
Innovation Solution
The imaging lens system consists of a negative first lens with a concave object-side surface, a positive second lens, a negative third lens, a positive fourth lens with a convex object-side surface, and a positive fifth lens, arranged in a specific configuration with a stop between the first and third lenses, adhering to specific focal length and curvature radius ratios to optimize power distribution and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all lenses are made of glass with spherical surfaces, then weather resistance and low cost are achieved, but optical performance and compactness are limited
Solution Approach 1:
The patent combines glass lenses (for weather resistance) with plastic lenses (for aberration correction and compactness). Specifically, the fourth lens is made of plastic with a convex object-side surface, allowing aspherical design for better optical performance while the glass lenses maintain environmental durability. This composite material approach resolves the contradiction between weather resistance and optical performance.
Solution Approach 2:
The patent introduces aspherical surfaces on plastic lenses (particularly the fourth lens with convex object-side surface) to correct spherical aberration and improve optical performance. The aspherical design allows better light ray control compared to traditional spherical glass lenses, achieving higher manufacturing precision while maintaining compactness.
2Illumination intensity
If a small F-number is achieved using plastic lenses, then low illumination photography is possible, but protection means is needed increasing cost
Solution Approach 1:
The patent uses a hybrid construction where plastic lenses (second, third, and fourth lenses) enable small F-number and low illumination capability, while glass lenses (first and fifth lenses) provide protection and weather resistance. This eliminates the need for additional cover glass protection, maintaining low cost while achieving high illumination performance.
3Volume of moving object
If the lens system is made compact, then small size is achieved, but back focus and telecentricity are compromised
Solution Approach 1:
The patent divides the lens system into five distinct lens elements with specific power distributions (negative first lens, positive second lens, negative third lens, positive fourth lens, positive fifth lens). This segmentation allows optimization of each element's function while maintaining overall compactness and achieving the required back focus and telecentricity through coordinated design.
Solution Approach 2:
The patent employs specific parameter relationships (f1/f = -0.5 to -1.5, f2/f = 0.3 to 0.7, f3/f = -0.3 to -0.7, f4/f = 0.2 to 0.6, f5/f = 0.4 to 0.8) to balance compactness with back focus and telecentricity requirements. By carefully controlling focal length ratios and curvature radii, the system achieves small size while maintaining operational performance.
4Manufacturing precision
If more lenses are added to improve optical performance, then high resolution is achieved, but device complexity and cost increase
Solution Approach 1:
The patent achieves high optical performance with only five lens elements by using composite materials (glass and plastic) with complementary properties. The plastic lenses provide effective aberration correction, reducing the need for additional lens elements, thereby maintaining low complexity while achieving high resolution.
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 the realization of a compact, cost-effective imaging lens with high telecentricity, long back focus, and small F-number, capable of producing high-resolution images even in low illumination conditions, while ensuring excellent weather resistance.
Implementation Method 1
a negative first lens L1 having a concave object-side surface, a positive second lens L2, a negative third lens L3, a positive fourth lens L4 having a convex object-side surface, and a positive fifth lens L5
Data Source
AI summary
An imaging lens consists of a negative first lens having a concave object-side surface, a positive second lens, a negative third lens, a positive fourth lens having a convex object-side surface, and a positive fifth lens, which are in this order from an object side. A stop is arranged between an image-side surface of the first lens and an object-side surface of the third lens. When the focal length of an entire system is f, and the focal length of the first lens is f1, and the focal length of the second lens is f2, the following formula is satisfied:−1.30<f1/f2>−0.65 (7).