Plastic Imaging Lens Diffractive Surface Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional imaging lenses composed of four lenses face challenges in achieving compactness, thinness, and wide angle of view while maintaining adequate aberration correction and manufacturability, particularly when applied to small image sensors like those in mobile terminals.
Innovation Solution
An imaging lens configuration with four lenses, where all lenses are made of plastic material and have aspheric surfaces, including a diffractive optical surface, with specific refractive index and Abbe number conditions to ensure adequate refractive power distribution and aberration correction, allowing for a short total track length and wide angle of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional four-lens configuration with negative power lens is used to correct chromatic aberration, then chromatic aberration correction is achieved, but the total track length increases making the lens thicker
Solution Approach 1:
The patent changes the fundamental parameter of chromatic aberration correction from using material dispersion differences (Abbe numbers) to using diffractive optical path differences. By forming a diffractive optical surface on at least one lens surface, the system achieves chromatic aberration correction through the wavelength-dependent diffraction effect rather than through material selection, thereby eliminating the need for negative power lenses and reducing total track length.
Solution Approach 2:
The patent replaces the traditional mechanical/optical system of using multiple lenses with different Abbe numbers and negative power elements to correct chromatic aberration with a diffractive optical surface that uses wave optics principles. This substitution allows chromatic aberration correction without increasing the mechanical length of the optical system.
2Manufacturing precision
If the number of constituent lenses is increased to increase pixel density capability, then imaging performance is improved, but the device becomes less compact and thicker
Solution Approach 1:
The patent uses composite optical structures by combining refractive optics (lenses with specific refractive indices and Abbe numbers) with diffractive optics (surfaces with microlens arrays or phase modulation patterns). This composite approach allows the four-lens system to achieve high pixel density imaging performance while maintaining compactness, as the diffractive surfaces add functional complexity without increasing physical size.
3Ease of manufacture
If all lenses are made of plastic material with aspheric surfaces, then manufacturing cost and ease of production are improved, but aberration correction becomes more challenging
Solution Approach 1:
The patent changes the approach to aberration correction by introducing diffractive optical surfaces that provide additional degrees of freedom in controlling optical path differences. This allows plastic lenses with aspheric surfaces to achieve adequate aberration correction by combining geometric optics (aspheric shapes) with wave optics (diffractive patterns), maintaining ease of manufacturing while improving optical performance.
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 a compact, thin imaging lens with a wide angle of view and effective aberration correction, suitable for high-pixel-density image sensors, while being cost-effective and manufacturable, with a total track length as short as 2.74 mm and a half angle of view of approximately 38.8 degrees.
Implementation Method 1
A diffractive optical surface is formed on at least one of the lens surfaces from the image-side surface of the first lens to the image-side surface of the second lens
Data Source
AI summary
An imaging lens includes, from the object side to the image side, an aperture stop, a first lens with positive refractive power having a convex object-side surface near an optical axis, a second lens with positive refractive power having a convex image-side surface near the axis, a third lens with positive refractive power having a convex image-side surface near the axis, and a fourth lens with negative refractive power having a concave image-side surface near the axis, wherein all lens surfaces are aspheric, all lenses are made of plastic material, a diffractive optical surface is formed on at least one of the lens surfaces from the first lens image-side surface to the second lens image-side surface, and at least one of the three positive lenses satisfies 1.58<Ndi where Ndi is the refractive index of the i-th positive lens at the d-ray.