Zoom Lens Four-Group Configuration for Digital Camera Imaging
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Solution Overview
Problem
Digital camera systems with interchangeable lenses require a zoom lens that is compact, capable of high-speed focusing for video shooting, and maintains high imaging performance, while existing zoom lenses are not suitable for digital camera applications due to inadequate optical performance and lens geometry.
Innovation Solution
A zoom lens configuration comprising a positive-negative-positive-negative four-group arrangement, where the first and third lens groups move towards the object plane during magnification changes, and the second and fourth lens groups move along the optical axis, with the fourth lens group configured as a single negative lens or cemented lens, optimizing lens geometry to satisfy specific curvature and focal length ratios for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a zoom lens is designed for film camera application, then it achieves compact size, but light rays enter the image plane at acute angles resulting in poor imaging performance for digital cameras
Solution Approach 1:
The patent changes the optical parameters of the zoom lens by introducing a positive lens group between the negative lens group and the image plane, transforming the light ray trajectory so that rays enter the image plane at angles close to vertical rather than acute angles, thereby improving imaging performance for digital camera sensors
2Speed
If the focusing lens group weight is reduced for high-speed video shooting, then focusing speed improves, but optical performance may deteriorate
Solution Approach 1:
The patent segments the lens system into multiple independent lens groups (positive lens group, negative lens group, fourth lens group) that can move independently. The focusing function is assigned to the fourth lens group which moves along the optical axis, while the positive and negative lens groups move toward the object plane during magnification changes, enabling high-speed focusing while maintaining optical performance
Solution Approach 2:
The patent implements dynamic movement patterns for different lens groups based on operational requirements: during magnification changes, the positive and negative lens groups move toward the object plane, while during focusing operations, only the fourth lens group moves along the optical axis, optimizing both speed and performance
3Adaptability or versatility
If a four-zoom type lens is designed mainly for film camera, then it achieves variable magnification, but it is not suitable for digital camera application due to acute angle light entry
Solution Approach 1:
The patent modifies the optical parameters by adding a positive lens group that redirects light rays to enter the image plane at angles close to vertical, making the variable magnification lens suitable for digital camera sensors while preserving the magnification variability function
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 size with high-speed focusing and high imaging performance, suitable for video shooting while maintaining optical quality, by optimizing the movement and curvature of lens groups within the zoom lens.
Implementation Method 1
a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having negative refractive power
Data Source
AI summary
A zoom lens includes: first to fourth lens groups having positive, negative, positive, and negative refractive power, respectively. The first to fourth lens groups are arranged in order from the object plane. The fourth lens group is configured of one negative lens or a cemented lens including positive and negative lenses that are arranged in order from object plane and are attached to each other. A magnification-varying operation from wide end to telephoto end causes the first and third lens groups to travel toward the object plane and causes the second and fourth lens groups to travel along an optical axis. A focusing operation causes the fourth lens group to travel along the optical axis. The following conditional expression is satisfied:0.7<(R4f+R4r)/(R4f−R4r)<5 (1)where R4f and R4r are radiuses of curvature of a most-object-sided and a most-image-sided optical surfaces, respectively, in the fourth lens group.