Compact Lens System with Aberration Control
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Solution Overview
Problem
Existing photographing lens systems for mirrorless interchangeable-lens cameras face challenges in miniaturization while maintaining high optical quality, often suffering from aberrations such as astigmatism, spherical aberration, and coma due to unsuitable refractive power balances and large numbers of lens elements, which also lead to increased size and weight.
Innovation Solution
A photographing lens system comprising a positive front lens group, an aperture diaphragm, and a positive rear lens group, with specific conditions on focal lengths and Abbe numbers to ensure miniaturization and correction of aberrations, including a negative cemented lens and a positive lens element in the rear group, and a focusing lens group with an aspherical surface for rapid focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a negative lens element is provided closest to the object side within the front lens group to attain a long backfocus, then the backfocus is extended, but the photographing lens system becomes larger in size
Solution Approach 1:
The patent applies parameter changes by precisely controlling the focal lengths of the front and rear lens groups (satisfying 0.35 < fF/fR < 1.5) and the refractive power of the negative lens element (satisfying -1.4 < fL1/f < 0.9). This optimization allows the backfocus to be extended to 0.20mm or more while keeping the total lens length compact, resolving the contradiction between backfocus length and lens system size.
2Reliability
If five lens elements are provided in the rear lens group, then aberrations can be corrected, but the entire optical system becomes enlarged
Solution Approach 1:
The patent reduces the number of lens elements in the rear lens group from five to three elements while maintaining effective aberration correction. This is achieved by optimizing the focal length ratio (0.35 < fF/fR < 1.5) and the negative lens element's refractive power (-1.4 < fL1/f < 0.9), which allows compact configuration with fewer elements to achieve the same optical performance.
Solution Approach 2:
The patent extracts and removes redundant lens elements from the rear lens group, reducing from five elements to three elements. By taking out unnecessary elements while maintaining the essential optical functions through optimized parameters, the optical system size is reduced while aberration correction capability is preserved.
3Length of stationary object
If a negative lens element is provided closest to the image side within the rear lens group to diverge peripheral light rays, then backfocus is extended, but spherical aberration, coma and astigmatism increase
Solution Approach 1:
The patent optimizes the refractive power of the negative lens element closest to the object side by controlling its focal length to satisfy -1.4 < fL1/f < 0.9. This parameter optimization ensures that the negative lens element provides sufficient backfocus (0.20mm or more) while maintaining appropriate light ray convergence, thereby preventing increases in spherical aberration, coma, and astigmatism.
4Volume of moving object
If the refractive power of the rear lens group is made too strong to reduce lens size, then astigmatism occurs
Solution Approach 1:
The patent balances the refractive power between the front and rear lens groups by controlling the focal length ratio to satisfy 0.35 < fF/fR < 1.5. This parameter balance prevents the rear lens group from having excessively strong refractive power, thereby avoiding astigmatism while still achieving lens system miniaturization through optimized configuration.
5Volume of moving object
If the refractive power of the front lens group is made too strong to reduce lens size, then spherical aberration and coma increase
Solution Approach 1:
The patent optimizes the refractive power distribution by controlling the focal length of the negative lens element in the front group to satisfy -1.4 < fL1/f < 0.9 and the focal length ratio to satisfy 0.35 < fF/fR < 1.5. This parameter optimization allows the front lens group to have sufficient refractive power for miniaturization while maintaining control over spherical aberration and coma through balanced optical design.
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 achieves a miniaturized lens system with superior optical quality by effectively correcting astigmatism, spherical aberration, and coma, enabling rapid focusing and preventing dust images from being sharply imaged, thus improving camera performance and size efficiency.
Implementation Method 1
a focusing lens group with an aspherical surface for rapid focusing
Implementation Method 2
at least two positive cemented lenses, in that order from the object side
Data Source
AI summary
A photographing lens system includes a positive front lens group, an aperture diaphragm, and a positive rear lens group, in that order from the object side. The front lens group includes at least one negative lens element, and at least two positive cemented lenses, in that order from the object side, and the following conditions are satisfied:0.35<fF/fR<1.5 (1),and−1.4<fL1/f<−0.9 (2),wherein fF and fR designate the focal lengths of the front lens group and the rear lens group, fL1 designates the combined focal length of the negative lens elements provided within said front lens group; and f designates the focal length of the entire photographing lens system.