Compact Zoom Lens Aberration Correction via Second Group Design
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Solution Overview
Problem
Existing zoom lens systems for digital still cameras face challenges in achieving high optical performance with miniaturization, as they often suffer from chromatic aberration and sensitivity issues due to the reduction in lens elements for compactness, and vibration reduction mechanisms can compromise optical performance.
Innovation Solution
A zoom lens system comprising a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group, where the second lens group is composed of at least two positive and one negative lens elements, with specific Abbe number and partial dispersion ratio conditions met, and includes aspherical surfaces to correct aberrations, and a vibration reduction mechanism that moves the second lens group perpendicular to the optical axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of lens elements is reduced to make the zoom lens system compact, then the size of the zoom lens system decreases, but chromatic aberration correction becomes insufficient
Solution Approach 1:
The patent applies parameter changes by carefully selecting the Abbe numbers and partial dispersion ratios of lens materials, and by optimizing the focal lengths and positions of lens elements. Specifically, the second lens group uses a positive lens with Abbe number 25-40 and partial dispersion ratio 0.52-0.56, combined with a negative lens having specific dispersion characteristics, to achieve effective chromatic aberration correction with a limited number of elements.
2Length of moving object
If the thickness of each lens group is reduced to achieve compactness, then the overall size decreases, but the number of lens elements must be reduced, making it impossible to sufficiently correct aberrations
Solution Approach 1:
The patent applies local quality by giving specific optical characteristics to the second lens group, which serves as the vibration reduction lens group. This group uses materials with specific Abbe numbers (25-40 for positive lens, 30-60 for negative lens) and partial dispersion ratios to provide both aberration correction and vibration reduction functionality within a compact form.
Solution Approach 2:
The second lens group is designed to perform multiple functions simultaneously: it acts as both the vibration reduction lens group that corrects camera shake and as the primary means for correcting chromatic and spherical aberrations. This multi-functionality allows the patent to achieve aberration correction without adding extra dedicated correction elements.
3Reliability
If a vibration reduction lens group is moved perpendicular to the optical axis to correct camera shake, then vibration reduction function is achieved, but decentering aberration, chromatic aberration and spherical aberration are generated
Solution Approach 1:
The patent applies preliminary action by pre-configuring the second lens group with specific material properties (Abbe number 25-40, partial dispersion ratio 0.52-0.56) and structural characteristics before the vibration reduction operation. This preliminary design ensures that when the group is decentered for vibration reduction, the inherent optical properties minimize the generation of decentering aberration, chromatic aberration, and spherical aberration.
Solution Approach 2:
The patent uses composite material principles by combining a positive lens element with specific dispersion characteristics (Abbe number 25-40, partial dispersion ratio 0.52-0.56) and a negative lens element with complementary properties in the second lens group. This composite structure provides both the positive and negative dispersion needed to correct chromatic aberrations that arise during vibration reduction operation.
4Volume of moving object
If the imaging device is miniaturized to increase portability, then the camera becomes more compact, but the received light amount of each pixel becomes low, lowering sensitivity
Solution Approach 1:
The patent addresses this contradiction by optimizing the optical parameters of the zoom lens system, including the aperture ratio and focal length relationships, to maximize light transmission efficiency. The conditional expressions for Abbe numbers and partial dispersion ratios are designed to minimize optical losses and maximize the light reaching the miniaturized imaging device pixels.
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 enables a compact zoom lens system with improved chromatic aberration correction, high resolution, and effective vibration reduction, maintaining optical performance across various focal lengths while ensuring compactness and sensitivity.
Implementation Method 1
at least one lens surface in the second lens group is an aspherical surface
Implementation Method 2
At least one positive lens element and the negative lens element in the second lens group satisfy the following conditional expressions (1) and (2): θgF2p>0.64−0.0016·νd2p (1) θgF2n<0.64−0.0016·νd2n (2) where θgF2p denotes a partial dispersion ratio of a material of the at least one positive lens element in the second lens group, νd2p denotes Abbe number of the material of the at least one positive lens element in the second lens group
Data Source
AI summary
Providing a compact zoom lens system having high optical performance suitable for an electronic imaging device with a large number of pixels. The zoom lens system includes, in order from an object, 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. When zooming from a wide-angle end state to a telephoto end state, the first lens group and the second lens group are moved such that a distance between the first lens group and the second lens group decreases, and a distance between the second lens group and the third lens group increases. The second lens group is composed of at least two positive lens elements and one negative lens element. At least one positive lens element and the negative lens element in the second lens group satisfy given conditional expressions.