Four-Element Image Pickup Lens with Glass and Plastic Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image pickup lenses face challenges in downsizing while maintaining high performance, particularly in achieving a wide angle of view and correcting various aberrations for image pickup elements with high pixel density, leading to issues with peripheral image quality and temperature-induced refractive index fluctuations.
Innovation Solution
A four-element image pickup lens structure with specific refractive power distributions and material choices, including glass and plastic lenses, is designed to ensure a wide angle of view, correct aberrations, and minimize temperature-induced image point fluctuations by using glass for the first and second lenses and plastic for the third and fourth lenses, with conditional expressions guiding lens curvature and refractive power settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an inverted-Ernostar type image pickup lens with a positive fourth lens is used, then the principal point position is improved, but the back focal length becomes long and downsizing is difficult
Solution Approach 1:
The patent changes the refractive power parameter of the fourth lens from positive (inverted-Ernostar type) to negative (telephoto type). This parameter change allows the back focal length to be shortened while maintaining acceptable principal point position, enabling lens downsizing without completely sacrificing optical performance.
Solution Approach 2:
The patent applies local quality by giving each lens element a specific refractive power sign (positive for 1st and 3rd lenses, negative for 2nd and 4th lenses) optimized for its position in the optical system. This local optimization allows the fourth lens to have negative refractive power, contributing to back focal length reduction while other lenses compensate to maintain overall optical quality.
2Device complexity
If only one lens with negative refractive power is used in a four-element structure, then the structure is simplified, but Petzval sum correction is difficult and peripheral image quality deteriorates
Solution Approach 1:
The patent changes the refractive power parameter of the fourth lens from positive to negative, increasing the count of negative power lenses from one to two. This parameter change enables better Petzval sum correction through the combined effect of multiple negative power lenses, improving peripheral image quality while maintaining a relatively simple four-element structure.
3Length of moving object
If the total length of the image pickup lens is shortened, then downsizing is achieved, but the angle of view becomes narrow and aberration correction becomes insufficient
Solution Approach 1:
The patent uses composite material strategy by combining glass lenses (1st and 2nd elements) with plastic lenses (3rd and 4th elements). This composite approach allows the plastic lenses to be molded with complex aspheric surfaces that effectively correct aberrations, while the glass lenses provide stable optical properties, achieving good aberration correction in a compact total length.
Solution Approach 2:
The patent employs aspheric surfaces (non-spherical curvature) on lens elements, particularly on the plastic 3rd and 4th lenses. These curved surfaces are optimized to correct various aberrations (spherical aberration, coma, astigmatism) while maintaining a short total length, allowing the lens to achieve wide angle of view and good image quality in a compact form.
4Stability of the object's composition
If glass materials are used for all lenses, then optical performance is stable, but temperature-induced refractive index fluctuations affect image quality
Solution Approach 1:
The patent uses composite materials by combining glass lenses (1st and 2nd elements with stable refractive index) and plastic lenses (3rd and 4th elements with different thermal characteristics). This composite material strategy creates a system where the thermal expansion and refractive index changes of plastic lenses compensate for those of glass lenses, reducing overall temperature-induced image point fluctuations while maintaining good 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
The solution provides a compact image pickup lens with excellent aberration correction and telecentricity, suitable for high-pixel-density image sensors, while maintaining stability across temperature changes by offsetting refractive index fluctuations.
Implementation Method 1
a first lens with a positive refractive power
Implementation Method 2
a second lens with a negative refractive power
Implementation Method 3
a third lens with a positive refractive power
Implementation Method 4
a fourth lens with a negative refractive power
Data Source
AI summary
Provided are a small image pickup lens which ensures a wide angle of view, permits various aberrations to be excellently corrected and is applicable to an image pickup element having a high pixel density, an image pickup apparatus using the image pickup lens, and a mobile terminal using the image pickup apparatus. The image pickup lens employs a structure which includes, in order from the object side, an aperture stop, a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with negative refractive power, and the image pickup lens is designed to satisfy predetermined conditional expressions.