Four-Element Plastic Lens System for Compact Imaging
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Solution Overview
Problem
Conventional compact imaging lens systems for portable electronic products fail to meet the higher image quality standards due to limitations in refractive power distribution, chromatic aberration correction, and manufacturing complexity, particularly with excessive use of spherical-surface glass lenses.
Innovation Solution
An optical imaging lens system comprising four lens elements with specific refractive powers and surface curvatures, including a first lens with positive refractive power, a second with negative refractive power, a third with positive refractive power, and a fourth with either negative or positive refractive power, along with an aperture stop positioned between the object and the first lens element, optimizing focal lengths and spacings to reduce total track length and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spherical-surface glass lenses are used to correct chromatic aberration, then chromatic aberration correction is improved, but the total track length increases and manufacturing complexity increases
Solution Approach 1:
The patent changes the material parameter from glass to plastic and the surface geometry parameter from spherical to aspheric. This allows achieving chromatic aberration correction with a compact total track length by utilizing the different refractive index characteristics and aberration correction capabilities of plastic aspheric lenses compared to traditional glass spherical lenses.
Solution Approach 2:
The patent employs composite optical design by combining multiple plastic lens elements with different refractive indices and Abbe numbers. This composite approach allows chromatic aberration correction typically achieved by glass-cemented doublets to be realized in a compact plastic lens system with reduced total track length.
2Reliability
If spherical-surface glass lenses are adhered together to form a doublet, then chromatic aberration correction is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the chromatic aberration correction function from the complex process of adhering glass lenses together and integrates it into a single molded plastic lens element. This eliminates the need for complex multi-step manufacturing processes including lens fabrication, alignment, and adhesive bonding, while maintaining aberration correction performance.
Solution Approach 2:
The patent adopts plastic lens material that can be molded directly into the final form, replacing expensive and labor-intensive glass lens fabrication and assembly. The molded plastic lenses are cost-effective and simplify manufacturing, eliminating the need for complex adhering processes while achieving the required optical performance.
3Ease of manufacture
If conventional three lens element systems are used, then manufacturing is simpler, but image quality does not meet higher standards
Solution Approach 1:
The patent uses composite plastic lens materials with different optical properties to achieve superior image quality. By combining multiple plastic elements with varying refractive indices and dispersion characteristics, the system corrects multiple aberration types simultaneously, meeting high image quality standards while maintaining manufacturing simplicity through injection molding processes.
Solution Approach 2:
The patent employs aspheric surface profiles on the lens elements to correct spherical aberration and other monochromatic aberrations that cannot be corrected by spherical surfaces alone. The aspheric surfaces provide additional degrees of freedom in optical design, enabling high image quality performance while maintaining a compact four-element structure that is manufacturable by modern molding techniques.
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 system achieves reduced total track length, improved image quality, and increased photosensitivity by effectively correcting aberrations and positioning the principal point away from the image plane, while allowing for compact design and efficient manufacturing.
Implementation Method 1
a fourth lens element having a concave image-side surface, and at least one of the object-side and image-side surfaces thereof being aspheric
Data Source
AI summary
This invention provides an optical imaging lens system in order from an object side to an image side including: a first lens element with positive refractive power having a convex object-side surface and a concave image-side surface, a second lens element with negative refractive power having a convex object-side surface and a concave image-side surface, a third lens element with positive refractive power, and a fourth lens element having a concave image-side surface, and at least one of the object-side and image-side surfaces thereof being aspheric; wherein the optical imaging lens system further comprises an aperture stop and an electronic sensor on which an object is imaged, and the aperture stop is positioned between an object and the first lens element; wherein there are four lens elements with refractive power. By such arrangement, total track length and photosensitivity of the optical imaging lens system can be effectively reduced while retaining high image quality.