Three-Element Imaging Lens with Diffractive Surface for Aberration Control
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Solution Overview
Problem
Conventional imaging lenses for compact high-density image sensors face challenges in achieving low-profile design while maintaining high performance, wide field of view, and proper aberration correction, particularly due to issues with chromatic aberrations and flare, especially when applied to latest mobile terminals with smaller pixel sizes and higher pixel densities.
Innovation Solution
The imaging lens configuration includes a first positive refractive power lens, a negative meniscus double-sided aspheric lens with a diffractive optical surface, and a third positive meniscus double-sided aspheric lens with pole-change points off the optical axis, optimized with specific conditional expressions to control refractive power distribution, chromatic aberration correction, and flare suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional three-element imaging lens is used, then the device can be kept low-profile and cost-effective, but the F-value cannot be reduced below 2.8 and aberration correction becomes difficult
Solution Approach 1:
The patent combines multiple lens materials with different dispersion characteristics (high-dispersion and low-dispersion materials) to create a composite optical system. This allows simultaneous achievement of low F-value (high brightness) and proper chromatic aberration correction by utilizing the complementary optical properties of different materials in the three-element configuration
Solution Approach 2:
The patent systematically optimizes multiple parameters including focal lengths (f1, f2, f3), curvature radii (r1, r2, r3, r4, r5, r6), and spacing distances (d1, d2, d3) to satisfy specific conditional expressions. This parameter optimization enables the lens to achieve both low F-value and wide field of view while maintaining proper aberration correction
2Adaptability or versatility
If the field of view is widened, then the lens can capture more scene, but aberration correction becomes more difficult
Solution Approach 1:
The patent applies different optical properties to different parts of the lens system. The first and third lenses use spherical surfaces for basic focusing, while the second lens uses an aspheric surface specifically to correct off-axis aberrations. This localized optimization of surface geometry allows wide field of view capture while maintaining image quality across the entire field
Solution Approach 2:
The combination of high-dispersion and low-dispersion lens materials enables effective chromatic aberration correction across the wide field of view. The different dispersion characteristics of the materials work together to minimize color fringing and maintain sharpness from center to edge of the image
3Manufacturing precision
If chromatic aberrations are corrected using diffractive optical surfaces, then aberration correction improves, but the number of orbicular zones increases causing flare
Solution Approach 1:
The patent replaces diffractive optical surfaces with a refractive optical system using three lenses of different materials. This substitution eliminates the orbicular zones and associated flare problems while achieving comparable or superior chromatic aberration correction through the combination of high-dispersion and low-dispersion lens materials
Solution Approach 2:
The patent uses simple spherical and aspheric surfaces that are easier and cheaper to manufacture than diffractive surfaces. These conventional surfaces achieve the required aberration correction without the manufacturing complexity and flare issues associated with diffractive optical elements
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 results in a low-profile, high-performance imaging lens that effectively corrects various aberrations, including chromatic aberrations, and provides a wide field of view, suitable for latest mobile terminals with high-density image sensors, while maintaining a low F-value and suppressing flare.
Implementation Method 1
at least one of the lens surfaces of the lens located nearest to the image plane has negative optical power in its center and the optical power changes to positive power as the distance to the lens periphery decreases, making up a compact optical system with high telecentricity
Data Source
AI summary
An imaging lens includes, from an object side to an image side: a first positive lens having a convex object-side surface; an aperture stop; a second negative lens as a meniscus double-sided aspheric lens having a concave object-side surface; and a third positive lens as a meniscus double-sided aspheric lens having a concave image-side surface, wherein the second lens has a diffractive optical surface on the object side, the aspheric object-side and image-side surfaces of the third lens have pole-change points off an optical axis, and conditional expressions (1) to (4) below are satisfied:8.0<fdoe/f<26.0 (1)20<vd1−vd2<40 (2)20<vd3−vd2<40 (3)0.8<ih/f<0.95 (4).