Five-Lens Imaging System Compactness F-Number Optimization
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Solution Overview
Problem
Existing imaging lenses for compact devices like cellular telephones and smart phones have large F numbers, making it difficult to achieve high resolution and compact size simultaneously due to their design, which is not compatible with the increasing pixel density of imaging elements.
Innovation Solution
A five-lens configuration with specific refractive powers and shapes, including a biconvex first lens, negative second and third lenses, a positive fourth lens, and a biconcave fifth lens with inflection points, optimized to satisfy certain conditional expressions for focal lengths and radii of curvature, allowing for a small F number and high imaging performance while minimizing the total lens length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional five-lens configuration is used, then the lens can be compact, but the F number becomes too large for high-resolution imaging
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive powers, curvatures, and spacing of the five lens elements. Specifically, it sets the focal length ratio f/f4 between 2.0 and 3.5, and the curvature ratio R1f/R1r between 1.5 and 3.0, which enables achieving a small F number while maintaining compact lens volume. The biconvex first lens and biconcave fifth lens with inflection points are configured with specific parameter ranges that resolve the contradiction between compactness and low F number.
2Measurement precision
If the number of pixels in the imaging element is increased, then high resolution is achieved, but the pixel size is reduced requiring a smaller F number
Solution Approach 1:
The patent addresses this contradiction by changing the optical parameters of the lens system to achieve a small F number (Fno. < 2.5) that matches the requirements of high-pixel-density imaging elements. The specific configuration of five lenses with optimized refractive powers and the biconvex first lens combined with biconcave fifth lens creates an optical system that delivers sufficient illumination intensity for small pixels while maintaining high resolution imaging performance.
3Length of moving object
If the total lens length is reduced for compact devices, then the lens is more suitable for mobile devices, but imaging performance may deteriorate
Solution Approach 1:
The patent resolves this contradiction through careful parameter optimization of the five-lens configuration. By setting specific ranges for focal lengths, curvatures, and spacing between elements, the design achieves a short total lens length suitable for mobile devices while maintaining excellent imaging performance. The biconvex first lens and biconcave fifth lens with inflection points are positioned and sized to correct aberrations effectively within the compact form factor.
Solution Approach 2:
The patent employs curved surface designs, particularly the biconvex first lens and biconcave fifth lens with inflection points, to optimize light path control within the compact structure. The specific curvature ratios and aspheric surfaces enable effective aberration correction in a short lens configuration, maintaining imaging performance despite the reduced total 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 enables high-resolution imaging with a small F number and reduced lens length, suitable for compact devices, effectively addressing the limitations of previous lens designs by optimizing each lens element's configuration and shape.
Implementation Method 1
a first lens having a biconvex shape, a second lens having a negative refractive power, a third lens having a negative refractive power and a convex surface that faces the object side, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power
Data Source
AI summary
The imaging lens substantially consists of a first lens having a biconvex shape, a second lens having a negative refractive power, a third lens having a negative refractive power and a convex surface that faces the object side, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power, of which at least one of the object-side surface and the image-side surface has at least one inflection point, in this order from the object side; and wherein conditional expression (1A): −0.38<f/f45<−0.01 is satisfied. This conditional expression is related to the focal length f of the entire system and the combined focal length f45 of the fourth lens and the fifth lens.