Camera Optical Lens with Free-Form Seventh Lens for Aberration Correction
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Solution Overview
Problem
Conventional camera optical lenses with rotational symmetric aspheric surfaces struggle to correct off-axis aberrations effectively, leading to insufficient ultra-thinning and wide-angle capabilities, and inadequate imaging performance in night scenes and background bokeh.
Innovation Solution
A camera optical lens design comprising seven lenses, including a first lens with negative refractive power, a seventh lens with negative refractive power featuring free-form surfaces, and specific refractive indices and focal lengths that satisfy certain relational expressions to enhance optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rotational symmetric aspheric surfaces are adopted, then manufacturing is easier, but off-axis aberrations cannot be corrected well
Solution Approach 1:
The patent applies asymmetry by transitioning from rotational symmetric aspheric surfaces to free-form surfaces for the seventh lens. The free-form surface breaks the rotational symmetry, allowing independent control of sagittal and tangential planes, which enables effective correction of off-axis aberrations while maintaining manufacturability through modern free-form machining and molding technologies.
2Device complexity
If conventional lens structure is used, then design is simpler, but ultra-thinning and wide-angle extent are insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive indices of all seven lenses within specific ranges (e.g., 1.56≤nd3≤1.59, 1.53≤nd6≤1.81, 1.61≤nd7≤1.67) and configuring focal lengths to satisfy specific relational expressions. This systematic parameter optimization enables ultra-thinning (reduced total optical length) and wide-angle performance while maintaining manageable design complexity through structured relationships between parameters.
3Ease of manufacture
If rotational symmetric aspheric surfaces are used, then processing is easier, but imaging quality in night scenes and background bokeh is insufficient
Solution Approach 1:
The patent applies asymmetry by implementing free-form surfaces on the seventh lens to replace rotational symmetric aspheric surfaces. This asymmetric free-form design provides additional degrees of freedom for correcting off-axis aberrations, thereby improving imaging quality in night scenes and background bokeh, while modern free-form processing technologies maintain reasonable processing ease.
4Manufacturing precision
If free-form surfaces are added, then aberration balance and imaging quality improve, but processing difficulty increases
Solution Approach 1:
The patent applies asymmetry through free-form surfaces that break rotational symmetry, providing superior aberration correction and imaging quality. To mitigate processing difficulty, the design confines free-form surfaces to specific lens elements (seventh lens) rather than all surfaces, and uses systematic parameter relationships to simplify the overall manufacturing process.
Solution Approach 2:
The patent applies local quality by selectively applying free-form surfaces only to the seventh lens rather than all lens elements. This localized approach concentrates the complexity where it is most needed for aberration correction, while other lenses maintain simpler rotational symmetric aspheric surfaces, thereby balancing imaging quality improvement with processing feasibility.
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 lens achieves excellent optical characteristics with a large aperture, wide field of view, ultra-thinning, low optical distortion, and low SMIA TV distortion, making it suitable for high-pixel mobile phone camera lenses and web camera lenses.
Implementation Method 1
a seventh lens having negative refractive power, wherein an object side surface and an image side surface of the seventh lens are free-form surfaces
Implementation Method 2
a refractive index of the third lens is nd3; a refractive index of the sixth lens is nd6; a refractive index of the seventh lens is nd7
Data Source
AI summary
Provided is a camera optical lens including seven lenses sequentially from object side to image side: first lens having negative refractive power, second lens having positive refractive power, third lens having positive refractive power, fourth lens having positive refractive power, fifth lens having negative refractive power, sixth lens having positive refractive power, seventh lens having negative refractive power and with object and image side surfaces being free-form surfaces. Focal length of camera optical lens is f; focal length of first lens is f1, focal length of third lens is f3, focal length of fourth lens is f4; refractive index of third lens is nd3; refractive index of sixth lens is nd6; refractive index of seventh lens is nd7, and following relational expressions are satisfied: −1.52≤f1/f≤−1.38; 1.56≤nd3≤1.59; 1.53≤nd6≤1.81; 1.61≤nd7≤1.67; 2.04≤f3/f4≤2.27. The camera optical lens has excellent optical characteristics, and has large aperture, wide field of view, ultra-thinning and low optical distortion.