Three-Lens Optical System Miniaturization via Aspheric Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical lens systems for digital cameras face challenges in miniaturization due to long back focal lengths and limited design freedom for correcting aberrations, particularly off-axis aberrations, which affect image quality and mechanical structure size.
Innovation Solution
A three-lens optical system with a meniscus first lens element of positive refractive power, a meniscus second lens element with negative refractive power and aspheric surfaces, and a meniscus third lens element with negative refractive power and aspheric surfaces, along with an aperture stop placement to balance refractive power and correct aberrations, using plastic materials for injection molding to reduce size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional three-lens system with a positive third lens element is used, then the system can form an image, but the back focal length becomes relatively long, resulting in a larger mechanical structure that cannot satisfy miniaturization requirements
Solution Approach 1:
The patent changes the refractive power parameter of the third lens element from positive to negative, which fundamentally alters the optical path and allows the back focal length to be shortened while maintaining imaging function. This parameter change enables the total track length to be reduced to satisfy miniaturization requirements.
Solution Approach 2:
The patent employs aspheric surfaces for the second and third lens elements, replacing traditional spherical surfaces. This allows for better control of light paths and aberrations, enabling compact design with reduced back focal length while maintaining image quality.
2Ease of manufacture
If spherical glass lens elements are used, then the lens system is easier to manufacture with conventional methods, but the degrees of freedom for correcting off-axis aberration are reduced, making it more difficult to control image quality
Solution Approach 1:
The patent introduces aspheric surfaces on the second and third lens elements, which provide additional degrees of freedom for correcting off-axis aberrations such as coma and distortion. The aspheric coefficients allow precise control of light paths across the field of view, significantly improving image quality compared to spherical surfaces.
Solution Approach 2:
The patent uses a combination of plastic materials with different Abbe numbers for the three lens elements. This material selection strategy enables effective correction of chromatic aberrations while maintaining compatibility with injection molding manufacturing processes, achieving both good image quality and manufacturing feasibility.
3Volume of moving object
If the aperture stop is located close to the object side to reduce total track length, then the system becomes more compact, but the exit pupil moves far from the image plane, affecting light projection angles and sensor photosensitivity
Solution Approach 1:
The patent optimizes the aperture stop position and the refractive powers of all three lens elements to achieve a balance. By carefully selecting the focal lengths and spacing, the system maintains a compact total track length while ensuring that the exit pupil position provides appropriate incident angles for the sensor, thereby preserving photosensitivity.
Solution Approach 2:
The patent designs each lens element with specific local properties - the first element with strong positive power for compactness, and the second and third elements with negative power and aspheric surfaces to correct aberrations and control the exit pupil position, achieving local optimization that resolves the global contradiction.
4Stability of the object's composition
If glass lens elements are used, then the optical properties are stable, but the production cost is higher and the system is harder to miniaturize compared to plastic materials
Solution Approach 1:
The patent selects plastic materials with specific refractive indices and Abbe numbers for the three lens elements. This material selection enables effective aberration correction while taking advantage of the manufacturing benefits of plastic injection molding, including lower cost, easier miniaturization, and the ability to create complex aspheric surfaces more economically than glass.
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 effectively reduces the total track length, improves image quality by correcting aberrations, and enhances photosensitivity while maintaining miniaturization and reducing production costs, achieving a shorter focal length and better field of view.
Implementation Method 1
a meniscus second lens element with negative refractive power having a convex image-side surface, the object-side surface and the image-side surface of the second lens element being both aspheric; a meniscus third lens element with negative refractive power having a convex object-side surface, the object-side surface and the image-side surface of the third lens element being both aspheric
Implementation Method 2
the aperture stop is located close to the object side, so that the total track length of the optical lens system will be effectively reduced and the exit pupil of the optical lens system will also be far away from the image plane. Therefore, the light will be projected onto the sensor with a relatively small incident angle
Data Source
AI summary
An optical lens system for taking image consisting of three lens elements with refractive power, in order from the object side to the image side: a meniscus first lens element with positive refractive power having a convex object-side surface; an aperture stop; a meniscus plastic second lens element with negative refractive power having a convex image-side surface, and the object-side surface and the image-side surface of the second lens element being both aspheric, the Abbe number of the second lens element being V2, and it satisfying the relation: V2>40; a meniscus plastic third lens element with negative refractive power having a convex object-side surface, the object-side surface and the image-side surface of the third lens element being both aspheric, an Abbe number of the third lens element being V3, and it satisfying the relation: V3>40.