Zoom Lens with Plastic Aspherical Elements for Compact Wide-Angle Design
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Solution Overview
Problem
Conventional zoom lenses for digital cameras and video cameras face challenges in achieving a wide angle of view and high zoom ratio while maintaining a compact size and low cost, often resulting in narrow angles of view and low zoom ratios due to the use of fewer lenses and plastic lenses, which increases manufacturing costs when incorporating aspherical lenses.
Innovation Solution
A zoom lens configuration comprising a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with positive refractive power, where the first lens group includes a negative and a positive lens, the second lens group includes a cemented lens with one positive and one negative lens, and the third lens group includes a single positive lens, with specific focal length and refractive index conditions to optimize image forming performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an aspherical lens is used for the negative lens in the first lens group, then the image forming performance and aberration correction are improved, but the manufacturing cost increases dramatically
Solution Approach 1:
The patent changes the parameter of lens material by using a plastic lens with aspherical surface instead of glass aspherical lens, which maintains the aberration correction performance while significantly reducing manufacturing cost. The conditional expression (3) on refractive index and Abbe number is optimized to achieve this balance.
Solution Approach 2:
The patent replaces expensive glass aspherical lenses with cheaper plastic aspherical lenses that can be manufactured more economically, accepting that plastic lenses have different optical properties but achieving sufficient performance through optimized design parameters.
2Weight of stationary object
If fewer lenses are used to decrease weight and cost, then the lens system becomes lighter and cheaper, but the angle of view becomes narrow and zoom ratio becomes low
Solution Approach 1:
The patent optimizes the refractive index and Abbe number parameters of the plastic lenses to achieve high zoom ratio and wide angle of view with a reduced number of lenses. The conditional expressions (1), (2), (4), (5), (6), and (7) are designed to balance optical performance with compact lens structure.
Solution Approach 2:
The patent uses composite lens structures combining plastic lenses with aspherical surfaces and cemented lens groups to achieve multiple functions (wide angle of view, high zoom ratio, aberration correction) within a compact and lightweight design.
3Volume of moving object
If a zoom lens with compact size is designed, then the camera main unit becomes smaller, but the aberration correction becomes difficult to maintain across various focal lengths
Solution Approach 1:
The patent divides the lens system into three distinct lens groups (first lens group with negative refractive power, second lens group with positive refractive power, and third lens group with positive refractive power), where each group is optimized for specific functions. This segmentation allows compact overall size while maintaining aberration correction through coordinated design of individual groups.
Solution Approach 2:
The patent uses conditional expressions to precisely control the refractive indices, Abbe numbers, and surface curvatures of each lens group to maintain aberration correction across the zoom range. The aspherical surface parameters are optimized to correct aberrations in the compact lens configuration.
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 good image forming performance with a wide angle of view and high zoom ratio, achieving compact size and low cost by optimizing the refractive powers and lens group movements, while maintaining effective aberration correction across various focal lengths.
Implementation Method 1
a first lens group having negative refractive power; a second lens group having positive refractive power; and a third lens group having positive refractive power, wherein at least the first lens group and the second lens group moving along the optical axis respectively upon zooming
Implementation Method 2
the second lens is a plastic lens having an aspherical surface
Data Source
AI summary
A zoom lens ZL comprising a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power, wherein the first lens group G1 includes a first lens having negative refractive power and a second lens which is a plastic lens having positive refractive power, the second lens group G2 includes a third lens having positive refractive power, a fourth lens having positive refractive power and a fifth lens having negative refractive power, the third lens group G3 includes a sixth lens having positive refractive power, and the conditional expressions: 1.50<(−f1)/fw<2.52, 0.4<(−f1)/fL2 <0.8, n2×n2×ν2<77.0 are satisfied respectively.