Compact 4-Element Image Pickup Lens with Aspheric Aberration Correction
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Solution Overview
Problem
Conventional image pickup lenses in 4-element structures face challenges in downsizing while maintaining aberration correction, particularly due to limited negative refractive power and increased back focus, which complicates peripheral image correction and compatibility with larger pixel image pickup elements.
Innovation Solution
An image pickup lens configuration with a 4-element structure, comprising an aperture stop, a first positive lens, a second negative lens with a concave surface, a third lens with aspheric surfaces for aberration correction, and a fourth lens with aspheric surfaces, satisfying specific curvature radius and refractive power conditions to achieve downsizing and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a 4-element lens structure is used to improve aberration correction, then image quality is improved, but the total lens length increases making downsizing difficult
Solution Approach 1:
The patent applies parameter changes by carefully controlling the curvature radius of the second lens surface (r4) and the refractive power of the third lens (P3) to satisfy specific conditional expressions. This allows the lens to achieve excellent aberration correction while maintaining a compact total length suitable for mobile terminals.
Solution Approach 2:
The patent introduces aspheric surfaces on the third and fourth lenses to correct aberrations more effectively. The aspheric shapes allow for better control of light rays across the entire image field, achieving high image quality in a compact 4-element structure.
2Manufacturing precision
If the fourth lens is made positive to improve image side performance, then back focus increases, but this is disadvantageous for downsizing
Solution Approach 1:
The patent optimizes the refractive power distribution among the four lenses, specifically controlling the third lens's refractive power (P3) relative to the total system power (P) to satisfy |P3/P| < 0.7. This parameter control allows the fourth lens to be positive while keeping back focus short, resolving the contradiction between image performance and compactness.
3Device complexity
If only one lens has negative refractive power, then the structure is simple, but Petzval's sum correction becomes difficult reducing peripheral image quality
Solution Approach 1:
The patent maintains structural simplicity with only the second lens having negative refractive power, while achieving excellent Petzval's sum correction through precise parameter control of the third lens's refractive power and the curvature of the second lens surface. This resolves the contradiction between simplicity and peripheral correction capability.
4Length of moving object
If total lens length is shortened to achieve downsizing, then compactness is improved, but lens performance deteriorates
Solution Approach 1:
The patent introduces aspheric surfaces on the third and fourth lenses to compensate for the performance loss that would normally result from shortening the total lens length. The aspheric shapes enable effective aberration correction in a compact configuration, achieving both downsizing and maintained performance.
Solution Approach 2:
The patent satisfies specific conditional expressions for the curvature radius (r4/f > 0.2) and refractive power distribution (|P3/P| < 0.7) to optimize the compact 4-element structure, ensuring excellent aberration correction is achieved despite the shortened total length.
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 configuration effectively corrects various aberrations, secures excellent image forming performance, and enables a shorter total lens length, making it suitable for smaller-sized mobile terminals with larger pixel image pickup elements.
Implementation Method 1
a third lens comprising an aspheric surface; and a fourth lens comprising an aspheric surface
Data Source
AI summary
An image pickup lens is provided for forming an image of an object on a photoelectrical converter of a solid-state image pickup element. The image pickup lens includes, in order from an object side thereof: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power and including a concave surface facing an image side of the image pickup lens; a third lens including an aspheric surface; and a fourth lens including an aspheric surface. The image pickup lens satisfies predetermined conditions relating to a curvature radius of the surface of the second lens facing the image side and a refractive power of the third lens.