Imaging Lens with Hybrid Diffractive Refractive Elements
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Solution Overview
Problem
Conventional imaging lenses in mobile devices face challenges in achieving a balance between compactness, high resolution, wide field of view, and effective aberration correction, particularly with chromatic aberrations, due to limitations in plastic material options and the partial dispersion characteristics of high-dispersion materials.
Innovation Solution
A compact imaging lens configuration with a specific arrangement of lenses and diffraction optical surfaces, including a first diffraction optical surface on the first to third lenses and a second on the fourth lens, optimized to correct chromatic aberrations and maintain a short total track length, using a combination of positive and negative refractive power lenses and aspheric surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of constituent lenses is reduced to four for compactness, then the lens size is reduced, but the ability to correct aberrations deteriorates
Solution Approach 1:
The patent applies diffraction optical surfaces with specific optical path difference functions to lens surfaces, changing the optical parameters to achieve both compactness and aberration correction. The diffraction structures modify light propagation to correct chromatic and other aberrations without requiring additional lens elements.
Solution Approach 2:
The patent combines refractive optics with diffractive optics in a hybrid system. The diffraction optical surfaces are formed on plastic lens materials, creating a composite optical system that leverages both refractive and diffractive properties to achieve superior aberration correction in a compact form.
2Manufacturing precision
If high-dispersion materials are used to correct chromatic aberrations, then chromatic aberration correction is improved, but residual chromatic aberrations persist due to partial dispersion characteristics
Solution Approach 1:
The patent uses diffraction optical surfaces with specifically designed optical path difference functions to counteract the partial dispersion characteristics of plastic materials. By adjusting the diffraction structure parameters, the system achieves better chromatic aberration correction that overcomes the limitations of high-dispersion plastic materials.
3Length of stationary object
If the total track length is reduced for low-profile design, then the camera module thickness is reduced, but the field of view and imaging performance deteriorate
Solution Approach 1:
The patent employs diffraction optical surfaces that enable a short total track length while maintaining a wide field of view. The diffraction structures modify the optical path to achieve compact design without sacrificing imaging performance or field of view coverage.
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 provides a wide field of view, high brightness, and improved aberration correction, particularly for chromatic aberrations, while maintaining a low-profile design suitable for mobile devices, enhancing imaging performance.
Implementation Method 1
a diffraction optical surface with a chromatic dispersion function is formed on one of the object-side surface of the first lens to the object-side surface of the third lens
Data Source
AI summary
Designed for a solid-state image sensor, it includes, in order from an object side to an image side: a first positive lens having a convex object-side surface; a second negative lens having a concave image-side surface; a third positive meniscus lens having a convex image-side surface; and a fourth negative lens having concave object-side and image-side surfaces near an optical axis. A first diffraction optical surface is formed on one lens surface of the first to third lenses, and a second one is formed on the fourth lens object-side surface. The imaging lens satisfies a conditional expression below,0.0<r6/r7<0.1,where r6 denotes the curvature radius of the third lens image-side surface, and r7 denotes that of the fourth lens object-side surface.