Compact Optical System Layout for Shading and Aberration Control
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Solution Overview
Problem
Existing optical systems face challenges in achieving a short overall lens length while maintaining high optical performance, as they often suffer from increased aberrations and shading due to oblique light incidence on the image sensor, particularly when the aperture stop is positioned close to the imaging plane.
Innovation Solution
An optical system configuration comprising a specific arrangement of lenses and a diaphragm, with conditional expressions governing the distances and refractive properties, such as SPIP/TTL and PNdave, to balance lens length and performance, including aspherical surfaces on certain lenses to correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the aperture stop is positioned close to the imaging plane to shorten the overall lens length, then the overall lens length is reduced, but shading occurs due to oblique light incidence on the periphery of the image sensor
Solution Approach 1:
The patent positions the aperture stop asymmetrically closer to the object than to the image plane, breaking the symmetric arrangement. This asymmetric positioning allows the light beams to pass through the lens system with reduced oblique incidence angles at the image sensor periphery, thereby suppressing shading while maintaining a compact overall lens length.
Solution Approach 2:
The patent optimizes specific parameters including the distance between the aperture stop and the first lens (0.3×f to 0.8×f), the focal lengths of individual lenses, and the refractive indices of lens materials. By carefully adjusting these parameters, the system achieves a balance between short overall lens length and suppression of oblique incidence-induced shading.
2Object-affected harmful factors
If the aperture stop is positioned closer to the object than the center of the optical system to restrain shading, then shading is reduced, but it becomes difficult to satisfactorily correct various aberrations because the lens configuration becomes asymmetrical
Solution Approach 1:
The patent assigns different refractive powers and material properties to specific lenses in the asymmetric configuration. The first lens has positive refractive power, the second lens has positive refractive power, the third lens has negative refractive power, and subsequent lenses have specific powers designed to correct aberrations. This local differentiation of optical properties enables effective aberration correction despite the asymmetric aperture stop positioning.
Solution Approach 2:
The patent uses lens materials with different refractive indices (nd) and Abbe numbers (vd) to correct various types of aberrations. By combining materials with different optical properties in the asymmetric lens configuration, the system achieves both shading suppression and satisfactory aberration correction.
3Reliability
If various aberrations are corrected in a short overall lens length system, then optical performance is improved, but the number of lenses tends to increase
Solution Approach 1:
The patent designs each lens to perform multiple functions: the first and second lenses with positive refractive power contribute to focusing and aberration correction, the third lens with negative refractive power corrects spherical aberration and coma, and the fourth through sixth lenses further refine aberration correction while maintaining a compact structure. This multi-functional design allows effective aberration correction with a limited number of lenses.
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 proposed optical system achieves a short overall lens length with excellent optical performance by suppressing oblique incidence and effectively correcting various aberrations, facilitating compact camera designs.
Implementation Method 1
a first lens L1 having a positive refractive power, an aperture stop SP, a second lens L2 having a positive refractive power, and a third lens L3 having a negative refractive power
Implementation Method 2
an optical system L0 according to each example includes a plurality of lenses
Data Source
AI summary
An optical system includes a plurality of lenses and a diaphragm. The plurality of lenses consist of, in order from an object side to an image side, a first lens having a positive refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, a fourth lens, a fifth lens, and a sixth lens. The diaphragm is located between the first lens and the second lens. A predetermined condition is satisfied.