Zoom Lens Design with Spherical Lenses for Compact High-Zoom Ratio
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Solution Overview
Problem
Conventional zoom lenses with aspherical negative lenses are costly and large, making them unsuitable for compact, high-zoom ratio applications in digital cameras.
Innovation Solution
A zoom lens configuration comprising a first lens group with a negative spherical lens and a plastic positive lens separated by an air gap, a second lens group with three or fewer lenses including a plastic negative lens, and a third lens group, where specific focal length and Abbe number conditions are met to achieve a high zoom ratio while reducing size and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an aspherical lens is used as a negative lens in the first lens group, then optical performance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive aspherical lenses with spherical lenses that have simpler, cheaper manufacturing processes. The first lens group uses a negative spherical lens instead of a negative aspherical lens, and the second lens group uses a positive spherical lens and negative spherical lens instead of aspherical lenses, significantly reducing manufacturing costs while maintaining acceptable optical performance through optimized lens configurations and air gap arrangements.
Solution Approach 2:
The patent optimizes specific parameter ranges to achieve high zoom ratios with spherical lenses. The conditional expressions define precise ranges for focal lengths (f1, f2, f3), air gap distances (d1, d2), and lens group movements, allowing spherical lenses to perform as effectively as aspherical lenses in this specific configuration.
2Manufacturing precision
If conventional zoom lens designs are used, then optical performance is maintained, but lens size and weight increase
Solution Approach 1:
The patent divides the zoom lens into three distinct lens groups with specific functions: the first lens group (negative spherical lens) for wide-angle control, the second lens group (positive and negative spherical lenses) for zoom functionality, and the third lens group (positive spherical lens) for telephoto control. This segmentation allows each group to be optimized independently for minimal weight while maintaining overall optical performance.
Solution Approach 2:
The patent uses spherical lenses as simplified copies of aspherical lenses, achieving comparable optical performance through repeated use of spherical geometry in multiple lens groups rather than requiring complex aspherical surfaces, thereby reducing weight and manufacturing complexity.
3Ease of manufacture
If the number of lenses is reduced to lower cost, then manufacturing cost decreases, but achieving high zoom ratio becomes difficult
Solution Approach 1:
The patent employs dynamic movement of lens groups along the optical axis to achieve zoom functionality with fewer lenses. The first, second, and third lens groups move in coordinated fashion during zooming, with the air gaps between them changing dynamically, enabling a 3.5x zoom ratio despite using only seven spherical lenses total.
Solution Approach 2:
The patent creates a composite optical system combining spherical lenses with different refractive indices and focal lengths arranged in specific configurations. The combination of negative spherical lens (first group), positive spherical lens and negative spherical lens (second group), and positive spherical lens (third group) creates a composite system that achieves high zoom ratio with minimal lens count.
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
The solution results in a compact, high-quality zoom lens with a high zoom ratio, suitable for digital cameras, that is inexpensive and maintains good optical performance across temperature changes, effectively addressing the cost and size issues of conventional designs.
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
Implementation Method 2
the first lens group comprises only one negative spherical lens and one plastic positive lens separated by an air gap; the second lens group comprises three or fewer lenses, including one positive lens component and one plastic negative lens
Data Source
AI summary
A zoom lens includes, in order from an object, 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. The first lens group G1 comprises only one negative spherical lens (lens L11) and one plastic positive lens (lens L12) separated by an air gap. The second lens group G2 comprises three or fewer lenses, including a positive lens component (cemented lens comprising a lens L21 and a lens L22), and one plastic negative lens (lens L23). The following conditional expressions are satisfied: 0.50<f1PL/(−f2PL)<2.50 and 0.80<(−f1)/f2<1.35, where f1PL is a focal length of the plastic positive lens forming the first lens group G1, f2PL is the focal length of the plastic negative lens forming the second lens group G2, f1 is the focal length of the first lens group G1, and f2 is the focal length of the second lens group G2.