Five-Lens Optical System Reducing Vignetting via Principal Point Shift
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Solution Overview
Problem
Conventional compact imaging lens systems with four or five elements struggle to achieve high image quality, especially in portable electronic devices, due to vignetting effects and low relative illumination, which are exacerbated by off-axis incident light.
Innovation Solution
An optical image capturing lens system comprising five lens elements with specific refractive powers and surface curvatures, including a fifth lens element with stronger positive refractive power to position the principal point away from the image plane, effectively controlling off-axis incidence and improving peripheral illumination, thereby reducing vignetting and enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional four-lens element system is used, then the device complexity is reduced, but the image quality deteriorates due to vignetting and low relative illumination
Solution Approach 1:
The optical system is divided into five distinct lens elements, each with specific refractive powers and surface curvatures. The fifth lens element is specifically designed with stronger positive refractive power to position the principal point away from the image plane, effectively controlling off-axis incident light and reducing vignetting effects.
Solution Approach 2:
The patent specifies precise parameter ranges for the lens system, including focal length ratios (0.55 < f/f5 < 1.20), curvature radius ratios (0.80 < R9/R1 < 1.50 and 0.20 < (R5+R6)/(R5-R6) < 1.80), and refractive power distributions. These parameter optimizations enable effective control of off-axis aberrations while maintaining compact system design.
2Reliability
If a five-lens element system is used, then the image quality is improved, but the device complexity increases
Solution Approach 1:
The fifth lens element serves multiple functions: it positions the principal point away from the image plane, controls off-axis incident light, corrects aberrations, and improves relative illumination. This multi-functionality justifies the additional element by consolidating multiple optical corrections into a single component.
Solution Approach 2:
By optimizing specific parameter ranges including the focal length ratio (0.55 < f/f5 < 1.20) and curvature radius ratios, the patent achieves effective aberration control and improved image quality while keeping the system compact, thereby managing the complexity introduced by the fifth element.
3Reliability
If the fifth lens element has stronger positive refractive power, then the principal point is positioned away from the image plane, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the fifth lens element, including the focal length ratio (0.55 < f/f5 < 1.20) and curvature radius ratio (0.80 < R9/R1 < 1.50). These standardized parameter ranges facilitate manufacturing by providing clear design targets while achieving the goal of positioning the principal point away from the image plane.
Solution Approach 2:
The patent employs aspheric surfaces on the lens elements, particularly the fifth lens element, to achieve the required curvature profiles. Aspheric designs allow for better control of off-axis aberrations and positioning of the principal point while providing manufacturable surface geometries that balance optical performance with fabrication capabilities.
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 proposed lens system achieves improved image quality by effectively controlling off-axis aberrations and increasing relative illumination, reducing vignetting and enhancing the sensing efficiency of image sensors.
Implementation Method 1
a fifth lens element with positive refractive power having a convex object-side surface at a paraxial region... both of the object-side and image-side surfaces being aspheric... the fifth lens element with stronger positive refractive power, which is favorable for positioning the principle point away toward the image plane
Data Source
AI summary
This disclosure provides an optical image capturing lens system comprising: a positive first lens element having a convex object-side surface, a negative second lens element, a positive third lens element having a convex image-side surface, a fourth lens element having a concave object-side surface and a convex image-side surface; and a positive fifth lens element having a convex object-side surface at a paraxial region thereof, both of the object-side and image-side surfaces being aspheric, and at least one inflection point is positioned on at least one of the object-side and image-side surfaces thereof. When particular relations are satisfied, the angle at which light projects onto the image plane can be efficiently controlled for increasing the relative illumination and preventing the occurrence of vignetting.