Rear Aperture Stop Optical Lens System for Stray Light Control
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Solution Overview
Problem
Conventional miniaturized optical lens systems for camera mobile phones suffer from increased stray light and sensitivity due to the arrangement of the front aperture stop, which affects image quality and aberration correction.
Innovation Solution
A three-lens optical lens system with specific refractive power configurations and aspheric surfaces, including a first lens element with positive refractive power, a second lens element with negative refractive power, and a third lens element with positive refractive power, where the aperture stop is located between the first and second lens elements, reducing stray light and improving image quality by controlling light incidence angles and correcting aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the aperture stop is arranged at the front (object side) of the optical lens system, then the aberration correction is improved, but the stray light increases and the sensitivity of the optical lens system increases
Solution Approach 1:
The patent inverts the conventional arrangement by placing the aperture stop at the rear (image side) between the third lens element and the sensor, rather than at the front object side. This inversion maintains effective aberration correction while eliminating the harmful effects of increased stray light and sensitivity that occur with front aperture stop arrangement.
Solution Approach 2:
The patent introduces an intermediary structure (the rear aperture stop positioned between the third lens element and sensor) that mediates between the lens elements and the sensor. This intermediary placement allows the aperture stop to function as an aberration corrector while preventing direct line-of-sight stray light paths and reducing sensitivity to off-axis light.
2Measurement precision
If the pixel size of the sensor is reduced continuously to achieve higher resolution, then the resolution is improved, but the demand for image quality becomes increasingly urgent and more difficult to maintain
Solution Approach 1:
The patent changes the optical parameters of the lens system by using aspheric surfaces with specific coefficients (k1, k2, k3 values) and precise curvature radii (R1-R6) to optimize light transmission and aberration correction. These parameter optimizations enable the system to maintain high image quality even with reduced pixel sizes, supporting higher resolution without sacrificing quality.
Solution Approach 2:
The patent employs composite optical design combining multiple lens elements with different refractive indices and aspheric coefficients. This composite approach allows sophisticated aberration correction and light control that maintains image quality at smaller pixel sizes, addressing the increasing demand for quality alongside resolution improvement.
3Volume of moving object
If the optical lens system is miniaturized to reduce volume, then the size is reduced, but the focal length becomes very short requiring precise control of lens element curvature and size
Solution Approach 1:
The patent extensively uses aspheric surfaces with optimized curvature radii (R1=2.08945mm, R2=-0.86293mm, etc.) and aspheric coefficients to achieve compact focal lengths while maintaining manufacturable precision. The aspheric geometry allows for shorter focal lengths without requiring extremely tight tolerances on simple spherical surfaces, thus enabling miniaturization with practical manufacturing precision.
Solution Approach 2:
The patent applies different curvature radii and aspheric coefficients to different lens elements and surfaces according to their specific functional requirements. This localized optimization allows each lens element to contribute efficiently to the compact design, achieving miniaturization while keeping individual manufacturing precision requirements manageable through targeted design rather than uniform extreme precision throughout.
4Volume of moving object
If the focal length of the optical lens system is shortened to reduce size, then the volume is reduced, but the radius of curvature and lens element size must be very small making conventional grind method impossible
Solution Approach 1:
The patent replaces the conventional mechanical grind method with injection molding technology for fabricating the lens elements. This substitution is enabled by using plastic materials (first lens element: plastic, second lens element: plastic, third lens element: plastic) that can be precisely formed through injection molding, allowing complex aspheric surfaces and compact dimensions to be manufactured efficiently without the limitations of traditional mechanical grinding.
Solution Approach 2:
The patent employs plastic materials for all three lens elements, utilizing their suitability for injection molding fabrication. This material choice enables the production of compact lens elements with complex aspheric geometries through modern manufacturing processes, overcoming the limitation of conventional grind methods for small-radius curvature and miniaturized dimensions.
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 effectively improves image quality, reduces the volume of the optical lens system, and enhances photosensitivity while minimizing vignetting and aberrations, making it suitable for high-resolution and wide-angle applications.
Implementation Method 1
a first lens element with positive refractive power having a convex object-side surface and a convex image-side surface
Implementation Method 2
the object-side surface of the first lens element being aspheric
Data Source
AI summary
An optical lens system for taking image comprises three lens elements with refractive power, from the object side to the image side: a first lens element with positive refractive power having a convex object-side surface and a convex image-side surface, and the object-side surface being aspheric; a plastic second lens element with negative refractive power having a concave object-side surface and a convex image-side surface, and the front and image-side surfaces thereof being aspheric; a plastic third lens element with positive refractive power having a convex object-side surface and a concave image-side surface, the front and image-side surfaces thereof being aspheric; wherein an aperture stop is located between the first and second lens elements. By such arrangements, it can reduce the volume and sensitivity of the optical lens system, and furthermore can obtain higher resolution.