Aspherical Lens Aberration Correction Strategy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fixed focal length objective lenses fail to provide effective aberration correction for large field of view and high numerical aperture, particularly for full frame image sensors, with existing solutions not achieving sufficient modulation transfer function (MTF) values and substantial chromatic aberration correction.
Innovation Solution
A fixed focal length objective lens design incorporating multiple aspherical surfaces strategically positioned in aperture stop and field proximity spaces, along with a retrofocus configuration, utilizing low and anomalous dispersion glasses to correct spherical, coma, astigmatism, and distortion aberrations, and achieve high MTF values and chromatic aberration control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional refractive lens elements are used, then the lens structure is simple, but the aberration correction is insufficient for large field of view and high numerical aperture
Solution Approach 1:
The patent applies aspherical surfaces on lens elements to correct aberrations. Specifically, at least one lens element has an aspherical surface defined by mathematical equations (including conic constants and higher-order terms) to correct spherical aberration, coma, and other monochromatic aberrations, enabling high MTF values across large fields of view and high numerical apertures while maintaining a manageable lens structure
Solution Approach 2:
The patent uses optical glasses with different dispersion properties (including anomalous dispersion glasses) combined with aspherical surfaces. This composite approach combines refractive index variations with non-spherical geometries to achieve superior aberration correction for both chromatic and monochromatic aberrations in a single integrated lens design
2Manufacturing precision
If more lens elements are added to correct aberrations, then the aberration correction improves, but the lens becomes less compact
Solution Approach 1:
The patent divides the optical system into functional groups: a first lens group with negative refractive power (including the aperture stop) and a second lens group with positive refractive power. This segmentation allows efficient aberration correction distribution across groups, achieving high MTF values while maintaining a compact retrofocus configuration suitable for wide-angle applications
Solution Approach 2:
By implementing aspherical surfaces on strategically positioned lens elements within the segmented groups, the patent achieves comprehensive aberration correction (spherical, coma, astigmatism, distortion) without requiring additional lens elements, thus maintaining compactness while achieving MTF values of at least 70% on axial field and 50% on other field points
3Illumination intensity
If high numerical aperture is achieved, then light gathering capability improves, but spherical aberration and coma increase
Solution Approach 1:
The patent employs aspherical surfaces with specifically optimized profiles (defined by conic constants and higher-order aspherical terms) on lens elements positioned in the light path. These surfaces are designed to counteract the increased spherical aberration and coma that result from high numerical aperture, enabling the lens to maintain MTF values of at least 70% on the axial field even at high aperture settings
Solution Approach 2:
The aspherical surfaces are strategically positioned on specific lens elements where they have the greatest impact on correcting spherical aberration and coma. The aperture stop is positioned in the first lens group to locally control ray heights, and aspherical surfaces are applied to elements where HC/HM ratios maximize their corrective effect on off-axis aberrations
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 lens design achieves MTF values of at least 70% on the axial field and 50% at all other field points, with substantial chromatic aberration correction, maintaining compactness and optimal focusing capabilities.
Implementation Method 1
a first lens group LG1 of negative refractive power, and a second lens group LG2 following of positive refracting power
Implementation Method 2
utilizing low and anomalous dispersion glasses to correct spherical, coma, astigmatism, and distortion aberrations
Data Source
AI summary
The invention consists of a fixed focal length objective lens forming an image of an object with a plurality of lens elements and an aperture stop (114), wherein the aperture stop (114) defines an aperture stop proximity space (118) and at least one field proximity space (120, 122). The objective lens comprises at least three aspherical surfaces (124, 126, 128, 130) of a lens element. Either two aspherical surfaces (128, 130) are positioned in the aperture stop proximity space (118) and at least one aspherical surface (124, 126) is positioned in a field proximity space (120, 122). Or at least one aspherical surface (128, 130) is positioned in the aperture stop proximity space (118) and two aspherical surfaces (124, 126) are positioned in a field proximity space (120, 122). This distribution of aspherical surfaces provides for means of optimally correction aberrations leading to a very high level of aberration correction.