Compact Wide-Angle Optical System With Large Aperture and Retractable Barrel
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Solution Overview
Problem
Conventional wide-angle lenses have a limited aperture of about 2.8, and there is a need for an optical system that combines compactness, wide-angle view, high tele-centricity, and large aperture while maintaining high performance.
Innovation Solution
The optical system consists of a first lens group with positive refractive power, an aperture stop, and a second lens group, where specific conditional expressions are satisfied to ensure the focal lengths and refractive indices of the lens components are optimized, allowing for a compact design with a wide-angle view and large aperture, including the use of negative and positive lens components with specific surface shapes and refractive indices, and at least one aspherical surface in the second lens group.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional wide-angle lens design is used, then the lens can achieve a wide angle of view, but the aperture is limited to about 2.8 and cannot be enlarged
Solution Approach 1:
The lens is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power) and individual lens components with specific arrangements. This segmentation allows each group to contribute differently to the overall optical performance, enabling larger aperture while maintaining wide-angle characteristics and controlling aberrations.
Solution Approach 2:
Different lens components have specifically designed local properties: the first lens group has positive refractive power with specific focal length ratios, the second lens group has negative refractive power, and individual lens surfaces have specific curvatures (including aspherical surfaces). These localized quality variations enable the system to achieve large aperture while correcting aberrations and maintaining compactness.
2Volume of moving object
If the lens barrel is made retractable for compactness, then the camera size is reduced, but maintaining high performance with large aperture and wide-angle view becomes difficult
Solution Approach 1:
The lens barrel is designed to be retractable, allowing the lens assembly to move between extended and retracted positions. The optical design compensates for the changes in optical path length and angle of view that occur during retraction, maintaining consistent imaging performance across different positions. This dynamic capability enables compact storage while preserving optical quality.
Solution Approach 2:
The lens barrel structure allows the lens components to be nested or folded into a compact configuration when retracted. The multiple lens groups and components are arranged to fit within a reduced volume when not in use, similar to nested dolls, while maintaining the ability to extend to the required optical path length for full performance operation.
3Illumination intensity
If the focal length of the first lens group is increased to achieve larger aperture, then the aperture size increases, but the lens becomes less compact and tele-centricity decreases
Solution Approach 1:
The design optimizes the focal length parameter of the first lens group relative to the total system focal length (satisfying 0.35 < fG1/f < 0.65) and the total length parameter (satisfying 2.0 < TL/f < 3.5). By carefully controlling these parameter ratios rather than simply increasing absolute focal length, the system achieves larger aperture while maintaining compact overall length and appropriate tele-centricity.
Solution Approach 2:
The lens groups have asymmetric arrangements with the first lens group having positive refractive power and the second having negative refractive power. The focal lengths and positions are asymmetrically distributed rather than symmetric, allowing optimization of aperture size independent of overall lens length. This asymmetric configuration enables the first lens group to contribute to aperture size while the second lens group compensates to maintain compactness.
4Reliability
If multiple lens components with specific configurations are added to achieve large aperture and wide-angle view, then optical performance improves, but the device complexity increases
Solution Approach 1:
The complex optical system is segmented into two main lens groups with distinct functions: the first lens group (positive refractive power) handles field curvature and distortion, while the second lens group (negative refractive power) controls chromatic aberration and spherical aberration. This functional segmentation manages complexity by organizing multiple components into coherent groups with specific roles.
Solution Approach 2:
The design specifies particular parameter ranges for the lens components (focal length ratios, total length ratios, refractive indices, Abbe numbers) that must be satisfied to achieve the desired performance. By defining these parameter constraints, the complexity of designing and manufacturing multiple lens components is managed through quantitative guidelines rather than trial-and-error approaches.
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 achieves a compact optical system with a wide-angle view of about 65°, a large aperture (2.0 Fno), and high tele-centricity, effectively correcting various aberrations and enabling the lens barrel to retract into the camera, maintaining high performance.
Implementation Method 1
a first lens group having positive refractive power, an aperture stop, and a second lens group... Each of the lens components may be constituted by a single lens or a cemented lens... where n21 denotes a refractive index of an optical material
Data Source
AI summary
Provided is an optical system having, in order from an object, a positive first lens group (G1), an aperture stop (S) and a second lens group (G2), wherein the first lens group (G1) includes, in order from the object, a negative lens component (L1), a positive lens component (L2) and a first lens component (L3, L4), the image side surface of which is a concave surface facing the aperture stop (S), the second lens group (G2) includes, in order from the object, a second lens component (L5, L6), the object side surface of which is a concave surface facing the aperture stop (S), and a positive lens component (L8) disposed closest to the image, the first lens component (L1) and the second lens component (L2) face each other sandwiching the aperture stop (S), and the following conditional expressions (1) and (2) are satisfied: 1.5<fG1/f<2.6 . . . (1) and 2.1<TL/f<3.1 . . . (2), where fG1 denotes a focal length of the first lens group (G1), f denotes a focal length of the optical system (WL), and TL denotes a distance on the optical axis, from the optical surface closest to the object to the optical surface closest to the Image in the optical system (WL).