Imaging Lens Diffractive Element Aberration Correction
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Solution Overview
Problem
Imaging lenses with long focal lengths face challenges in reducing size and weight while effectively correcting chromatic aberration and spherical aberration, as these corrections often lead to increased system size and weight.
Innovation Solution
The design incorporates a diffractive optical element with a positive and negative lens configuration, where the diffractive surface is positioned between the object and image sides, and specific conditional expressions are satisfied to optimize the placement and refractive properties of lenses, ensuring reduced size and weight while effectively correcting aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focal length of the imaging lens is increased, then the imaging performance is improved, but the size and weight of the optical system increase
Solution Approach 1:
The optical system is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, third lens group with positive refractive power) separated by air gaps. This segmentation allows each group to contribute differently to the overall focal length while keeping individual components smaller and lighter, resolving the contradiction between long focal length and reduced weight.
2Measurement precision
If chromatic aberration and spherical aberration are corrected by adding more lens elements, then optical performance is improved, but the size and weight of the system increase
Solution Approach 1:
The patent utilizes diffractive optical elements with specific diffraction coefficients and refractive index variations to correct chromatic and spherical aberrations. By changing the optical parameters (refractive index, diffraction coefficient) rather than simply adding more lens elements, the system achieves effective aberration correction while maintaining a compact and lightweight structure.
3Measurement precision
If the difference in height between principal rays on the diffractive surface is reduced, then chromatic aberration correction is improved, but the system size reduction becomes more difficult
Solution Approach 1:
The patent employs asymmetric lens designs where the first, second, and third lens groups have different refractive powers and are positioned at different distances from the image plane. This asymmetric configuration allows the principal ray height difference on the diffractive surface to be controlled for effective chromatic aberration correction while optimizing the overall system size through non-uniform distribution of 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 allows for a compact imaging lens that satisfactorily corrects chromatic and spherical aberrations, achieving a balance between size reduction and optical performance.
Implementation Method 1
an optical system comprising a diffractive optical element
Data Source
AI summary
The imaging lens consists of, in order from the object side, a front group, an aperture stop, and a rear group. The front group includes a diffractive optical element having a positive lens and a negative lens in order from the object side. A diffractive surface is provided between an object side surface of the positive lens and an image side surface of the negative lens. Assuming that a distance on an optical axis from the diffractive surface to the aperture stop in a state in which an object at infinity is in focus is Ddoe, and a focal length of the whole system in a state in which the object at infinity is in focus is f, the imaging lens satisfies Conditional Expression (1): 0.02<Ddoe/f<0.11.