Four-Lens Camera Optical System with Plastic Aspherical Elements
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Solution Overview
Problem
Existing optical systems for cameras with a wide-angle view face challenges in miniaturization and cost due to the use of plastic lenses with lower optical performance, requiring a large number of lenses and failing to provide optimal conditions for compactness and affordability, especially in monitoring applications where temperature changes affect lens contraction and expansion.
Innovation Solution
An optical system with four lenses, including a first meniscus-shaped lens with negative refractive power, a second convex lens with negative refractive power, a third convex lens with positive refractive power, and a fourth convex lens with positive refractive power, where the second and fourth lenses are formed as plastic lenses with aspherical surfaces, and an aperture stop and infrared filter are used to achieve a wide-angle view while compensating for temperature-induced changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plastic lenses are used to reduce cost and enable miniaturization, then manufacturing cost and size are reduced, but optical performance deteriorates
Solution Approach 1:
The patent uses plastic lenses with aspherical surfaces, combining the cost and molding advantages of plastic materials with the optical correction capabilities of aspherical design. This composite approach (plastic material + aspherical shape) resolves the contradiction by achieving acceptable optical performance through geometric correction rather than relying solely on material properties.
Solution Approach 2:
The patent specifically employs aspherical surfaces on the plastic lenses to correct optical aberrations. The aspherical curvature compensates for the lower inherent optical quality of plastic materials, allowing the system to achieve wide-angle performance with fewer lenses while maintaining image quality.
2Device complexity
If the number of lenses is reduced for miniaturization, then device size and complexity are reduced, but design freedom and optical performance deteriorate
Solution Approach 1:
The patent divides the optical system into four distinct lens elements with specific refractive power assignments (negative, negative, positive, positive). This segmentation allows each lens to be optimized for specific functions while working together as a compact unit, achieving wide-angle performance without requiring more lenses.
Solution Approach 2:
The patent changes key parameters including the use of aspherical surfaces, specific refractive power distributions, and the ratio of positive to negative lenses. These parameter changes enable the compact four-lens design to achieve wide-angle performance that would traditionally require more lenses.
3Weight of stationary object
If plastic lenses are used instead of glass lenses, then cost and weight are reduced, but temperature stability deteriorates
Solution Approach 1:
The patent addresses temperature stability by carefully selecting plastic materials with appropriate thermal expansion coefficients and designing the lens system with compensation mechanisms. The specific arrangement of positive and negative lenses helps compensate for thermal effects, maintaining optical performance across temperature variations.
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 and cost-effective optical system with improved image resolution and wide-angle view, effectively addressing the limitations of previous designs by minimizing lens count and maintaining performance across varying temperatures.
Implementation Method 1
a first lens L1 having a meniscus shape convex toward an object side and having a negative refractive power, a second lens L2 having a negative refractive power and having a convex surface toward the object side, a third lens L3 having a positive refractive power and having a convex surface toward the object side, and a fourth lens L4 having a positive refractive power and having a convex surface toward an image side
Implementation Method 2
inter-compensation can be achieved with respect to contraction and expansion of plastic lenses caused by external temperature
Implementation Method 3
inter-compensation can be achieved with respect to contraction and expansion of plastic lenses caused by external temperature
Data Source
AI summary
The present invention provides an optical system for a camera including: a first lens which has a negative refractive power and has a meniscus shape convex toward object side; a second lens which has a negative refractive power and has a convex surface toward object side; a third lens which has a positive refractive power and has a convex surface toward object side; and a fourth lens which has a positive refractive power and has a convex surface toward image side, wherein the optical system satisfies the following inequalities: 0.3<v3/v2<0.8, and 0.06<f1/TL/0.2, where v2 indicates an Abbe number of the second lens, v2 indicates an Abbe number of the third lens, f1 indicates the overall focal distance of lens system, and TL indicates a distance from a vertex of the object side of the first lens to an imaged plane.