Lens System with Segmented Negative Group for Brightness and Focus Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a demand for a normal-type image pickup system that is brighter and has minimal fluctuation in angle of view due to focusing, which existing wide-angle lens systems fail to provide effectively.
Innovation Solution
A lens system with a negative-positive-positive-positive four-group retrofocus configuration, where the first lens group has a telephoto-type configuration with a positive-negative arrangement of powers, and the second lens group moves during focusing, while a stop is fixed between the third and fourth lens groups to maintain constant F number and reduce angle of view fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a retrofocus-type wide-angle lens system is used, then it is easy to obtain bright images, but the focal length is extended beyond normal-type requirements and angle of view fluctuates during focusing
Solution Approach 1:
The first lens group with negative refractive power is divided into two sub-lens groups separated by a distance. The first sub-lens group includes a positive lens closest to the object side and a negative lens closest to the image plane side, creating a telephoto-type configuration within the negative power group. This segmentation allows the system to maintain retrofocus brightness characteristics while achieving normal-type focal length and reducing angle of view fluctuation during focusing.
2Illumination intensity
If the first lens group has negative refractive power for retrofocus configuration, then brightness is improved, but aberration correction becomes more difficult
Solution Approach 1:
Dividing the negative refractive power group into two sub-lens groups with specific spacing enables better control of light paths and aberration distribution. The telephoto-type configuration within the first sub-lens group further aids in correcting aberrations while maintaining the retrofocus structure for brightness.
Solution Approach 2:
The first sub-lens group is designed with specific local characteristics (positive lens followed by negative lens) to correct aberrations in the object side region, while the second sub-lens group handles other aberration components. This local optimization of lens properties improves overall aberration correction in the retrofocus system.
3Adaptability or versatility
If a multi-group lens system is used to correct aberrations and achieve normal focal length, then focal length suitability is improved, but device complexity increases
Solution Approach 1:
The lens system is organized into four main groups with the first group further segmented into two sub-groups. This hierarchical segmentation achieves normal-type focal length and reduced angle of view fluctuation while keeping the overall structure manageable through clear group definitions and functional assignments.
Solution Approach 2:
The first lens group with negative refractive power serves multiple functions: it establishes the retrofocus configuration for brightness, contains the telephoto-type sub-configuration for normal focal length, and through its segmentation enables aberration correction. This multi-functionality reduces the need for additional dedicated components.
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 provides a brighter image pickup system with minimal fluctuations in angle of view and focus, achieving a focal length suitable for standard lenses with improved aberration correction and reduced weight and size of moving lens groups.
Implementation Method 1
a first lens with positive refractive power that is disposed closest to the object side
Implementation Method 2
a second lens group that has positive refractive power and moves during focusing
Data Source
AI summary
A lens system (10) for image pickup includes, in order from an object side (11), a first lens group (G1) that has negative refractive power and is fixed during focusing, a second lens group (G2) that has positive refractive power and moves during focusing, a third lens group (G3) that has positive refractive power and is fixed during focusing, and a fourth lens group (G4) that has a stop disposed on the object side, is disposed closest to an image plane side, has positive refractive power, and is fixed during focusing. The first lens group includes a first lens (L11) with positive refractive power that is disposed closest to the object side.