Compact Lens System Design with High Refractive Index Elements
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Solution Overview
Problem
Existing lens systems with F numbers ranging from 1.4 to 2.4 face challenges in size reduction due to increased total length, chromatic aberration, and manufacturing difficulties with GRIN lenses, leading to larger and less compact designs.
Innovation Solution
A compact and fast lens system is achieved by using a positive lens element closest to the object side, a diaphragm in the widest air space, and multiple lens elements with refractive indices greater than 1.85, satisfying specific conditions for size reduction and aberration correction, including the use of aspheric surfaces and refractive index distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If GRIN lenses are used to reduce the number of lens elements, then the lens system is reduced in size, but the length of the front lens unit increases relative to the total length
Solution Approach 1:
The patent changes the refractive index parameter by using lens elements with refractive indices of 1.85 or higher, which allows for more compact lens design. This parameter change enables the lens system to achieve both reduced overall size and balanced front unit length by utilizing materials with higher light-bending capability, thereby resolving the contradiction between compactness and front unit proportion.
2Reliability
If a diaphragm is disposed in the widest air space in a large-diameter lens system, then chromatic aberration is compensated, but the distance from the object-side lens surface to the diaphragm increases
Solution Approach 1:
The patent uses lens elements with refractive indices of 1.85 or higher to change the optical parameters of the system. This allows the diaphragm to be positioned more effectively in the optical path, achieving aberration correction while maintaining a shorter distance from the object-side lens surface to the diaphragm, thus resolving the contradiction between aberration correction and compact design.
3Volume of moving object
If the lens system is designed to be compact with F number of 1.4 to 2.4, then the lens system size is reduced, but manufacturing precision requirements increase due to high refractive index materials
Solution Approach 1:
The patent specifies refractive indices of 1.85 or higher for the lens elements, which enables compact lens system design. By carefully selecting and controlling the refractive index parameter within specific ranges, the patent achieves a balance between compactness and manufacturability, ensuring that the lens system remains small while maintaining feasible manufacturing precision requirements through optimized material selection.
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 results in a compact lens system with improved size reduction and aberration correction, maintaining an F number of 1.4 to 2.4, while suppressing astigmatic differences and field curvature, facilitating a smaller diaphragm mechanism and reduced lens system size.
Implementation Method 1
a lens element closest to an object side is a positive lens element
Implementation Method 2
a diaphragm is disposed in a widest air space in the lens system
Implementation Method 3
two or more lens elements each having a refractive index equal to or greater than 1.85
Data Source
AI summary
It has conventionally been difficult to reduce the size of a fast lens system having an F number of about 1.4 to 2.4. In a lens system of the present invention, a positive lens element is disposed closest to an object side. A diaphragm is disposed in a widest air space in the lens system. The lens system of the present invention satisfies the following conditions: 0.05<L_1/L-TH<0.21 1.5<L-TH/Y<8 where L_1 is an interval from a lens surface located closest to the object side to a lens surface located on the object side relative to the diaphragm; L_TH is an interval from the lens surface located closest to the object side to a lens surface located closest to an image side; and Y is a maximum image height.