Compact Optical System Aberration Correction via Refractive Index Optimization
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Solution Overview
Problem
In optical systems for imaging apparatuses, such as digital cameras, there is a challenge in achieving satisfactory optical performance across the entire screen while minimizing the system size, as increasing refractive power to downsize the system leads to difficulties in correcting field curvature and other aberrations.
Innovation Solution
The optical system employs six or fewer lenses, including positive lenses and a final lens with negative refractive power, where specific conditions on total optical length, half-angle of view, and refractive indices are met to optimize lens configuration, ensuring effective correction of aberrations like field curvature, spherical aberration, and chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If refractive power of each positive lens is increased to downsize the optical system, then the optical system size is reduced, but field curvature correction becomes difficult and optical performance at the perimeter of the screen deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully controlling the refractive indices of lenses (specifically the relationship between np1, np2, and np3) and the total optical length TL to achieve optimal field curvature correction while maintaining compact size. The conditions 0.70 < np2/(np1+np3) < 1.30 and 0.40 < TL/(f×tanω) < 2.00 represent parameter optimization to resolve the contradiction between small size and aberration correction.
Solution Approach 2:
The patent uses composite materials by combining lenses with different refractive indices (np1, np2, np3) to achieve both compact size and proper field curvature correction. The use of multiple materials with specific refractive index relationships allows the system to maintain small dimensions while correcting optical aberrations that would otherwise be difficult to control.
2Volume of moving object
If the number of lenses is reduced to downsize the optical system, then the optical system becomes more compact, but aberration correction capability deteriorates
Solution Approach 1:
The patent applies universality by designing a three-lens system where each lens serves multiple functions. The first and second positive lenses and the third negative lens collectively address spherical aberration, field curvature, and chromatic aberration, allowing compact size while maintaining comprehensive aberration correction capability through multi-functional lens design.
Solution Approach 2:
The patent uses parameter changes by optimizing the refractive indices (np1, np2, np3) and the total optical length TL to achieve effective aberration correction with only three lenses. The specific parameter relationships (0.70 < np2/(np1+np3) < 1.30 and 0.40 < TL/(f×tanω) < 2.00) enable compact configuration while maintaining reliable 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
This configuration allows for a compact optical system with improved correction of aberrations, preventing under- or over-correction of field curvature and chromatic aberration, while maintaining a balanced refractive power distribution to achieve optimal image quality.
Implementation Method 1
an optical system includes six or less lenses, wherein the six or less lenses include a plurality of positive lenses, and a final lens having negative refractive power
Data Source
AI summary
An optical system includes six or less lenses, wherein the six or less lenses include a plurality of positive lenses, and a final lens having negative refractive power and disposed closest to an image, and wherein, where a total optical length obtained by addition of a back focus to a distance from a lens surface closest to an object in the optical system to a final lens surface is TL, a half angle of view is ω[°], a focal length of a whole system is f, and an average value of a refractive index of a lens having a highest refractive index and a refractive index of a lens having a second highest refractive index among the plurality of positive lenses is np12ave, following conditions are satisfied: 0.50<TL/(f×tan ω)<1.90, and 1.80<np12ave<2.20.