Imaging Optical System Aberration Correction via Refractive Power Distribution
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Solution Overview
Problem
Conventional wide-angle photographic lenses suffer from increased coma, astigmatism, and chromatic aberrations as the angle of view widens, and spherical aberrations become more pronounced with smaller F-numbers due to asymmetric refractive power arrangements and larger lens surface curvatures, making it difficult to achieve both a wide angle of view and small F-number while maintaining aberration correction.
Innovation Solution
The imaging optical system rearranges refractive power distribution by shifting negative refractive power to the object-side unit and increasing positive refractive power in the image-side unit, incorporating a third cemented lens with a negative lens on the reduction side to function as an aplanatic achromatic lens, and positioning the aperture stop closer to the reduction side to correct aberrations effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the angle of view is increased in conventional wide-angle photographic lenses, then a wider field of view is achieved, but coma, astigmatism, and chromatic aberration of magnification deteriorate due to asymmetric refractive power arrangement
Solution Approach 1:
The patent applies asymmetry by intentionally designing an asymmetric refractive power distribution where the object-side unit has positive refractive power and the image-side unit has negative refractive power. This asymmetric arrangement, combined with specific lens configurations including a cemented lens with concave surfaces facing both object and image sides, enables correction of coma, astigmatism, and chromatic aberration while achieving a wide angle of view of 70 degrees or more
Solution Approach 2:
The patent changes key optical parameters by setting the refractive power relationship between object-side and image-side units, positioning the aperture stop in the image-side unit, and designing specific lens curvatures. These parameter changes enable simultaneous achievement of wide angle of view and effective aberration correction
2Illumination intensity
If the F-number is decreased in conventional wide-angle photographic lenses, then a brighter image is achieved, but spherical aberration, coma, and longitudinal chromatic aberration occur more frequently due to larger lens surface curvatures
Solution Approach 1:
The patent changes the refractive power distribution parameters and aperture stop positioning to enable small F-number operation. Specifically, the object-side unit with positive refractive power and image-side unit with negative refractive power, combined with the aperture stop in the image-side unit, allows achieving F-number of 1.4 or smaller while correcting spherical aberration, coma, and longitudinal chromatic aberration through optimized lens surface curvatures
3Illumination intensity
If both wide angle of view and small F-number are achieved in conventional optical systems, then brightness and field of view are improved, but it becomes difficult to correct various aberrations effectively
Solution Approach 1:
The patent segments the optical system into distinct object-side unit and image-side unit with different refractive power characteristics. The object-side unit with positive refractive power handles light gathering and initial focusing, while the image-side unit with negative refractive power and containing the aperture stop handles aberration correction. This segmentation enables simultaneous achievement of wide angle of view, small F-number, and effective aberration correction
Solution Approach 2:
The patent introduces a cemented lens as an intermediary element with specific configuration (negative lens closest to image side with concave surface facing image side) that mediates between the object-side and image-side units. This intermediary lens configuration, combined with the aperture stop positioning, enables effective correction of multiple aberration types while maintaining wide angle of view and small F-number
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 favorable correction of various aberrations, enabling a wide angle of view exceeding 70° and a small F-number of about 1.2, while ensuring sufficient brightness and a long back focus, effectively addressing the limitations of conventional systems.
Implementation Method 1
an imaging optical system configured to form a conjugate relation between a conjugate point on an enlargement side having a long distance and a conjugate point on a reduction side having a short distance, the imaging optical system includes, in order from the enlargement side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit, and a fifth lens unit
Data Source
AI summary
An imaging optical system includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit, and a fifth lens unit, and the first lens unit includes a first negative lens and a first cemented lens, the second lens unit includes a second cemented lens and one or more positive lens components, the third lens unit includes one or more positive lens components and a third cemented lens, and the first cemented lens includes a negative lens closest to the reduction side and has a concave surface facing the reduction side, the second cemented lens has a positive refractive power and has a concave surface facing the enlargement side, the third cemented lens has a positive refractive power and has a negative lens on the reduction side.