Retrofocus Optical Layout for Distortion and Field Curvature Control
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Solution Overview
Problem
Existing optical systems face challenges in achieving compact size and high optical performance while effectively correcting distortion and curvature of field, particularly when using telephoto type power arrangements with limited lenses, leading to issues like pincushion distortion, large exit angles, and difficulty in correcting chromatic aberrations.
Innovation Solution
An optical system design comprising a retrofocus type power arrangement with a front group having negative refractive power and a rear group with positive refractive power, utilizing a meniscus-shaped final lens surface, and adhering to specific inequalities to optimize lens parameters such as TTL, PNdave, and sk/TTL, ensuring effective correction of distortion and curvature of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If telephoto type power arrangement is strengthened to reduce overall length, then compact size is achieved, but pincushion distortion and curvature of field increase
Solution Approach 1:
The patent applies parameter changes by carefully controlling the refractive powers and focal lengths of individual lenses within the optical system. Specifically, it sets the focal length of the first lens to satisfy 0.05 < f1/f < 0.15 and the second lens to satisfy -0.15 < f2/f < -0.05, where f is the focal length of the entire optical system. These parameter constraints allow the system to maintain a compact telephoto arrangement while correcting distortion and curvature of field.
Solution Approach 2:
The patent uses composite material principles by combining multiple lenses with different refractive indices and optical properties. The optical system includes at least four lenses with specific refractive powers arranged in a telephoto configuration, where each lens contributes differently to the overall optical performance. This composite approach allows correction of multiple aberrations simultaneously while maintaining compact size.
2Length of stationary object
If telephoto type power arrangement is strengthened to reduce overall length, then compact size is achieved, but exit angle of off-axis light beam becomes larger
Solution Approach 1:
The patent controls the exit angle parameter by setting specific constraints on the refractive powers of the first and second lenses. The focal length ratios f1/f and f2/f are constrained to specific ranges that simultaneously achieve compact overall length while limiting the exit angle of off-axis light beams to acceptable levels.
3Device complexity
If limited number of lenses is used in telephoto arrangement, then device complexity is reduced, but difficulty in correcting distortion and curvature of field increases
Solution Approach 1:
The patent achieves effective correction of distortion and curvature of field with a limited number of lenses (at least four) by precisely controlling the parameter ranges of each lens. The focal length ratios and refractive powers are optimized to work together synergistically, allowing correction of multiple aberrations with fewer elements than conventional designs.
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 solution enables a compact optical system with high performance by suppressing distortion and curvature of field, maintaining a balanced refractive index, and controlling the incident angle of off-axis light beams, thus enhancing image quality.
Implementation Method 1
A lens surface near an optical axis of the final lens has a meniscus shape with a convex surface on the object side
Data Source
AI summary
An optical system includes, in order from an object side to an image side, a front group, an aperture stop, and a rear group that has positive refractive power as a whole. The front group includes a first lens having negative refractive power disposed closest to an object. The rear group includes a final lens having positive refractive power disposed closest to an image plane. The optical system includes four or more lenses disposed between the first lens and the final lens. A lens surface near an optical axis of the final lens has a meniscus shape with a convex surface on the object side. Predetermined inequalities are satisfied.