Multi-Index Optical Element for Field Curvature Correction
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Solution Overview
Problem
Field curvature aberrations in optical systems lead to image blurring, especially at the edges of the image field, making it difficult to achieve sharp imaging across the entire object plane simultaneously, particularly with high numerical aperture front optical units.
Innovation Solution
An optical element with a planoconvex basic shape comprising three portions: a first portion with a plane side face for collecting radiation, a second portion with a convex side face for guiding rays to the image plane, and a third portion with a concave-convex form and higher refractive index than the other two portions, arranged directly adjacent to each other without gaps, to reduce field curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional front optical unit with high numerical aperture is used, then the light-gathering capability is improved, but field curvature aberration worsens causing image blurring at edges
Solution Approach 1:
The front optical unit is divided into multiple portions with different refractive indices (first portion with lower refractive index, second portion with higher refractive index). This segmentation allows each portion to contribute differently to ray bending, correcting field curvature while maintaining high numerical aperture for light gathering.
Solution Approach 2:
Different portions of the optical element are assigned different local optical properties (refractive indices). The first portion has a lower refractive index and the second portion has a higher refractive index, creating local variations in light bending capability that collectively correct the field curvature aberration across the image field.
2Manufacturing precision
If field curvature correction is attempted with conventional optical components, then image sharpness is improved, but the complexity of the optical system increases
Solution Approach 1:
Multiple optical functions (light gathering, focusing, and field curvature correction) are merged into a single integrated front optical unit. The different portions are contact-bonded together to form one compact element, eliminating the need for separate correction lenses or complex multi-element systems.
Solution Approach 2:
The optical element uses composite construction with portions made of materials having different refractive indices. These materials are contact-bonded without cement or adhesive, creating a composite optical structure that achieves aberration correction while maintaining simplicity.
3Manufacturing precision
If multiple optical components with different refractive indices are combined, then field curvature is reduced, but the risk of additional optical transitions and alignment errors increases
Solution Approach 1:
The different portions are contact-bonded directly to one another without introducing cement or adhesive layers. This merging approach eliminates additional optical transitions at the interfaces, reducing reflection losses and alignment errors while maintaining the beneficial refractive index differences for field curvature correction.
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 described optical element significantly reduces field curvature, allowing for improved image quality across the entire image field, easier correction of other aberrations, and the ability to achieve higher numerical apertures, such as up to NA=1.49.
Implementation Method 1
The plane side face of the first portion is designed to collect and steer a radiation to be captured into the optical element
Implementation Method 2
A refractive index of the third portion is greater than a refractive index of the second portion, wherein the refractive index of the second portion is greater than a refractive index of the first portion
Data Source
AI summary
An optical element comprises a planoconvex basic shape along an optical axis of the optical element; a third portion arranged between a first portion and a second portion. The first portion includes a plane side face for facing an object to be imaged. The second portion includes a convexly shaped side face for facing an image plane. The plane side face of the first portion is designed to collect and steer a radiation to be captured into the optical element, the optical element being designed to guide rays of the captured radiation in a beam path. The first, the second and the third portions are arranged directly adjacent to one another. A refractive index of the third portion is greater than a refractive index of the second portion, and the refractive index of the second portion is greater than a refractive index of the first portion.