Variable Focal Length Lens System Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional zoom lenses with high variable magnification ratios face challenges in achieving a wide angle of view of 75 degrees and high optical performance due to issues like spherical aberration and off-axis aberrations, particularly in the 'negative-precedence type' lenses, which require larger diameters and result in performance degradation.
Innovation Solution
A vari-focal length lens system comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group, where the distance between lens groups changes to correct aberrations, with aspherical surfaces and an aperture stop placement near the third lens group to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a negative-precedence type zoom lens is used to achieve high variable magnification ratio, then the zoom ratio increases, but the lens diameter increases and optical performance deteriorates due to spherical aberration and off-axis aberrations
Solution Approach 1:
The patent applies aspherical surfaces to specific lens surfaces (object-side surface of the positive lens in the first lens group, and image-side surfaces of positive and negative lenses in the second lens group) to correct spherical aberration. This changes the geometric parameter of the lens surfaces from spherical to aspherical, effectively reducing spherical aberration while maintaining the high zoom ratio capability of the negative-precedence type configuration.
Solution Approach 2:
The patent strategically places aperture stops at specific locations (between the first and second lens groups, and between the second and third lens groups) to control off-axis light rays locally. This local control of light paths corrects off-axis aberrations in critical regions without requiring a complete redesign of the entire lens system, thereby maintaining high zoom ratio while improving optical performance.
2Illumination intensity
If the aperture ratio is increased to reduce noise influence, then the light quantity reaching the light receiving element increases, but the lens size and complexity increase
Solution Approach 1:
The patent uses aspherical surfaces with specific curvature profiles to efficiently guide and concentrate light onto the light receiving element. The aspherical shapes optimize light paths to maximize light quantity delivery without requiring larger aperture dimensions, thereby increasing illumination intensity while avoiding proportional increases in lens size and complexity.
3Illumination intensity
If microlens array is placed in front of each light receiving element to guide light flux, then the light quantity increases, but the exit pupil position approaches the light receiving element causing off-axis light flux to form large angles with the optical axis
Solution Approach 1:
The patent introduces aperture stops as intermediary elements between the lens groups and the light receiving element. These aperture stops act as mediators that control and filter off-axis light rays before they reach the light receiving element, preventing large-angle off-axis flux from causing aberrations while still allowing sufficient on-axis light to pass through for adequate illumination.
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 wider angle of view while reducing lens size and correcting aberrations, ensuring high optical performance and compactness by satisfying specific conditional expressions for focal lengths and moving distances between lens groups.
Implementation Method 1
The object-side surface of the negative lens arranged on the object side and the object-side surface of the positive lens in the second lens group are formed in an aspherical shape
Data Source
AI summary
A vari-focal length lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. In the second lens group, each of the object-side surface of the negative lens arranged on the object side and the object-side surface of the positive lens is formed in an aspherical shape and satisfies the following conditional expression: 2.0<f1/(fw·ft)1/2<2.5 wherein f1 is a focal length of the first lens group, fw is a focal length in the whole lens system in a wide angle end state, and ft is a focal length in the whole lens system in a telephoto end state.