Imaging Lens with Single Moving Negative Lens for Fast Focusing
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Solution Overview
Problem
Current imaging lenses for digital cameras face challenges in achieving a small F number, wide angle of view, lightweight focusing lens groups, and fast focusing operations while maintaining high optical performance.
Innovation Solution
The design of an imaging lens comprising a specific configuration of lens groups with negative and positive refractive powers, including a first lens group with multiple negative lenses, a second group with two positive lenses, a third group with three positive lenses and a concave negative lens, and a fourth group consisting of a single moving negative lens, optimized by conditional formulas to achieve a small F number and wide angle of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a lens system is designed with a wide angle of view, then the angle of view is improved, but the F number becomes large (poor light gathering capability)
Solution Approach 1:
The lens system is divided into multiple lens groups (first negative lens group, second positive lens group, third positive lens group, fourth negative lens group) with different refractive powers. Each group contributes differently to the overall optical performance, allowing the system to achieve both wide angle of view and small F number through coordinated action of segmented components.
Solution Approach 2:
The patent employs specific parameter ranges for lens group configurations, including the ratio of focal lengths (0.3 < f1/f < -0.8), the number of lenses in each group, and the arrangement of positive and negative elements. These parameter optimizations enable simultaneous achievement of wide angle of view and small F number.
2Speed
If focusing lens groups are made lightweight for fast focusing, then focusing speed is improved, but optical performance may deteriorate
Solution Approach 1:
The focusing function is segmented to only the fourth lens group, which is designed as a lightweight single negative lens. This segmentation allows fast focusing movement while other lens groups remain stationary to maintain optical performance. The patent specifies that only the fourth lens group moves during focusing operations.
Solution Approach 2:
The fourth lens group is specifically designed with local quality optimized for focusing operations - it is made lightweight with a simple single-lens negative structure suitable for rapid movement. Other lens groups maintain more complex structures optimized for their respective optical functions, creating local quality differentiation across the system.
3Illumination intensity
If the F number is reduced for low light photography, then light gathering capability is improved, but optical performance becomes difficult to maintain
Solution Approach 1:
The patent optimizes multiple parameters simultaneously to achieve small F number while maintaining optical performance: the focal length ratio (0.3 < f1/f < -0.8), the specific arrangement of positive and negative lens groups, the number of lenses in each group, and the positioning of the aperture stop. These coordinated parameter changes enable F number reduction without optical performance degradation.
Solution Approach 2:
The lens system uses composite optical design combining multiple lens groups with different refractive powers and material properties. The combination of negative and positive lens groups creates a composite optical system that can achieve small F number while correcting various aberrations to maintain high optical performance.
4Reliability
If multiple lens groups are used to achieve small F number and wide angle, then optical performance is improved, but the weight of focusing lens groups increases
Solution Approach 1:
The focusing function is segmented to only the fourth lens group, which is designed as a lightweight single negative lens. This segmentation allows the majority of the optical power to be provided by stationary lens groups while the moving focusing group remains minimal in weight and complexity, enabling fast focusing without compromising overall optical performance.
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 the imaging lens to achieve a small F number, a wide angle of view, reduced weight of focusing lens groups, and fast focusing operations, while effectively correcting various aberrations for high optical performance.
Implementation Method 1
a first lens group having a negative refractive power as a whole; a second lens group having a positive refractive power as a whole; a third lens group having a positive refractive power as a whole; and a fourth lens group having a negative refractive power as a whole
Data Source
AI summary
An imaging lens is substantially constituted by: a negative first lens group; a positive second lens group; an aperture stop; a positive third lens group; and a negative fourth lens group; provided in this order from an object side. The first lens group is constituted only by two or more negative lenses. The second lens group has a positive lens at the most object side thereof. The third lens group has a negative lens having a concave surface toward the object side at the most object side thereof. The fourth lens group is constituted by a single negative lens. The fourth lens group moves from the object side to an image side when changing focus from an object at infinity to an object at an extremely close distance. Only the fourth lens group moves during focusing operations.