Three-Element Lens Assembly with Inverted Aperture Stop
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Solution Overview
Problem
Conventional image capturing lens systems face challenges in achieving a balance between field of view and total track length, with limited compactness and image quality, particularly in mobile devices.
Innovation Solution
A compact image capturing lens assembly comprising three lens elements with specific refractive powers and surface shapes, including aspheric surfaces, along with a stop placement that optimizes focal lengths, axial distances, and entrance pupil diameters to enhance field of view and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional three-element lens structure with front aperture stop is used, then the lens assembly can be compact, but the field of view is confined and cannot be enlarged
Solution Approach 1:
The patent inverts the conventional optical arrangement by placing the aperture stop between the first and second lens elements rather than at the front. This inversion allows the second lens element to effectively function as part of the entrance pupil, enabling a larger field of view without increasing the total track length. The stop position is specifically set to satisfy 0.30 < SD/TD < 0.70, where SD is the axial distance from the stop to the image-side surface of the third lens element and TD is the axial distance from the object-side surface of the first lens element to the image-side surface of the third lens element.
2Measurement precision
If the pixel size of sensors is reduced to achieve higher megapixels, then the sensor resolution is improved, but the optical system becomes more difficult to maintain compact size while preserving image quality
Solution Approach 1:
The patent employs aspheric surfaces on all six surfaces of the three lens elements, which allows for better control of optical aberrations at reduced optical system size. The aspheric coefficients are specifically optimized to maintain image quality for high-resolution sensors. Additionally, the ratio of focal lengths is controlled within specific ranges (f2/f3 between -0.50 and -0.10) to optimize the balance between compactness and image quality.
3Adaptability or versatility
If the refractive power distribution is optimized to enlarge field of view, then the field of view increases, but the total track length increases
Solution Approach 1:
The patent assigns specific refractive power characteristics to each lens element to optimize the overall system performance. The first lens element has positive refractive power, the second lens element has positive refractive power, and the third lens element has negative refractive power. This localized optimization of refractive powers, combined with the inverted stop position, enables a larger field of view without proportionally increasing the total track 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 solution effectively reduces the total track length, improves image quality, and increases the field of view, making it suitable for compact mobile devices while maintaining high image resolving power.
Implementation Method 1
The first lens element with positive refractive power has a convex object-side surface and a convex image-side surface, wherein the object-side surface and the image-side surface of the first lens element are aspheric
Data Source
AI summary
An image capturing lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element and a third lens element. The first lens element with positive refractive power has a convex object-side surface and a convex image-side surface, wherein the surfaces of the first lens element are aspheric. The second lens element with positive refractive power has a concave object-side surface and a convex image-side surface, wherein the surfaces of the second lens element are aspheric. The third lens element with negative refractive power has a concave image-side surface in a paraxial region thereof, wherein the image-side surface of the third lens element has at least one convex shape in an off-axis region thereof, and the surfaces of the third lens element are aspheric. The image capturing lens assembly has a total of three lens elements with refractive power.