Four-Element Aspheric Optical Lens for Compact Imaging
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Solution Overview
Problem
Conventional optical lenses for compact electronic devices face challenges in achieving a short total length and low manufacturing cost while maintaining high image quality and aberration correction, particularly due to complex lens designs and manufacturing difficulties.
Innovation Solution
The design of an optical lens with four sequentially arranged elements, each with specific refractive powers and surface curvatures, including a plastic third lens element with aspheric surfaces, and a fourth lens element with an inflection point, optimized by specific curvature and focal length relations to reduce total length and improve manufacturing ease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional optical lens design with four lens elements is used to achieve compact size and low cost, then the manufacturing cost is reduced and device complexity is lowered, but the total length of the lens becomes difficult to shorten further while maintaining good aberration correction
Solution Approach 1:
The patent applies aspheric surfaces to the third and fourth lens elements, replacing traditional spherical surfaces. This allows for better aberration correction in a compact design by varying the curvature across the lens surface, enabling shorter total length while maintaining image quality. The aspheric surfaces provide more degrees of freedom for optimizing the optical path and correcting field curvature and astigmatism.
Solution Approach 2:
The patent optimizes specific parameter relationships including the curvature radii ratios (R3-R4)/(R3+R4) and (R5-R6)/(R5+R6), the focal length ratio f3/f, and the thickness-to-focal-length ratio CT2/f. These parameter optimizations enable compact dimensions while maintaining aberration correction performance by carefully balancing the optical power distribution and physical dimensions of each lens element.
2Manufacturing precision
If the third lens element is designed with a convex object side turning into a concave shape at the edge (meniscus shape) to correct astigmatic field curving, then aberration correction is improved, but the lens shape becomes complicated and manufacturing difficulty increases
Solution Approach 1:
Instead of using a complex meniscus shape with drastic curvature changes, the patent employs aspheric surfaces on the third lens element that provide gradual curvature variation. This achieves astigmatic field curving correction through controlled aspheric coefficients rather than extreme geometric shapes, making the lens easier to manufacture while maintaining correction effectiveness.
Solution Approach 2:
The patent uses aspheric surface parameters (conic coefficients and higher-order terms) to control the curvature profile of the third lens element. This allows for precise control of the surface shape to correct astigmatism and field curvature without requiring drastic geometric changes, thereby simplifying manufacturing compared to traditional meniscus designs.
3Manufacturing precision
If the second lens element is made thicker to improve aberration correction, then image quality is enhanced, but the total length of the optical lens increases
Solution Approach 1:
The patent uses aspheric surfaces on multiple lens elements to improve aberration correction efficiency. This allows for thinner lens elements compared to spherical designs, as the aspheric profiles provide better control over light ray paths and reduce the need for increased thickness to achieve the same correction level.
Solution Approach 2:
The patent optimizes the thickness-to-focal-length ratio (CT2/f) of the second lens element within a specific range. This parameter optimization, combined with the aspheric surfaces on other elements, allows for reduced thickness while maintaining aberration correction performance, thereby shortening the total lens length.
4Device complexity
If a four-lens design is used instead of five or more lens elements to reduce manufacturing cost and device complexity, then production cost is lowered and device simplicity is improved, but achieving short total length with good aberration correction becomes more challenging
Solution Approach 1:
The patent introduces aspheric surfaces on the third and fourth lens elements to compensate for the reduced number of elements. The aspheric profiles provide additional degrees of freedom for aberration correction, enabling a compact four-element design to achieve performance that would traditionally require more elements, thereby shortening the total length while maintaining simplicity.
Solution Approach 2:
The patent optimizes multiple parameter relationships including curvature radii ratios, focal length ratios, and thickness-to-focal-length ratios to maximize the efficiency of each lens element. This parameter optimization enables a compact four-element configuration to achieve both short total length and good aberration correction, overcoming the limitations of reduced element count.
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
This configuration effectively shortens the optical lens, enhances aberration correction, and reduces manufacturing costs by using simpler lens elements, while maintaining high image quality and efficiency in image reception by the image sensor.
Implementation Method 1
the first lens element with positive refractive power has a convex object-side surface
Implementation Method 2
the second lens element with negative refractive power has a convex object-side surface and a concave image-side surface
Implementation Method 3
the plastic third lens element with positive refractive power has a concave object-side surface and a convex image-side surface, and both object-side surface and image-side surface thereof being aspheric
Implementation Method 4
the plastic fourth lens element with positive refractive power has a convex object-side surface and a concave image-side surface, and both object-side surface and image-side surface being aspheric
Data Source
AI summary
An optical lens for image pickup, sequentially arranged from an object side to an image side, comprising: the first lens element with positive refractive power having a convex object-side surface, the second lens element with negative refractive power having a convex object-side surface and a concave image-side surface, the plastic third lens element with positive refractive power having a concave object-side surface and a convex image-side surface with both being aspheric, the plastic fourth lens element with positive refractive power having a convex object-side surface and a concave image-side surface with both being aspheric. By such arrangements, the optical lens for image pickup satisfies conditions related to reduce the sensitivity and to shorten the total length for use in compact cameras and mobile phones with camera functionalities.