Retrofocus Imaging Optical System for Low Distortion Wide Angle
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Solution Overview
Problem
Retrofocus-type imaging optical systems face challenges in correcting distortion aberrations and achieving low distortion while maintaining a wide viewing angle, as they tend to increase aberrations due to asymmetrical alignment and negative refractive power, making it difficult to balance optical performance.
Innovation Solution
A single focal imaging optical system is designed with a first lens group having a negative refractive power and a second lens group with positive refractive power, including specific lens configurations such as negative and positive meniscus lenses, biconvex lenses, and biconcave lenses to correct aberrations and achieve a wide viewing angle with low distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a retrofocus-type imaging optical system with asymmetrical alignment and negative refractive power is used, then a wide viewing angle is achieved, but distortion aberrations increase
Solution Approach 1:
The patent applies asymmetry principle by configuring the first lens group with asymmetrical alignment where the optical axis does not coincide with the mechanical axis, and by using meniscus lenses with asymmetric curvature radii (R1 and R2 having different absolute values). This asymmetrical design enables wide viewing angle while controlling distortion aberrations through careful balancing of asymmetric elements
Solution Approach 2:
The patent employs parameter changes by optimizing specific curvature radii (R1, R2, R3, R4), air gaps (d1, d2, d3), and refractive indices (Nd1, Nd2, Nd3) to satisfy conditional expressions. By adjusting these parameters within specific ranges, the system achieves wide viewing angle with controlled distortion aberrations, transforming the trade-off into a balanced solution
2Length of stationary object
If a retrofocus-type imaging optical system with negative refractive power is used, then back focus space is secured for filters, but distortion aberrations are difficult to correct
Solution Approach 1:
The patent applies segmentation by dividing the imaging optical system into multiple lens groups (first lens group with negative power, second lens group with positive power, and third lens group). Each group is optimized independently to control aberrations while maintaining overall back focus distance, allowing distortion correction without sacrificing back focus space for filters
Solution Approach 2:
The patent introduces an intermediary element - the aperture stop positioned between the first and second lens groups - which acts as a mediator to control the path of light rays. This aperture stop helps manage distortion aberrations by limiting marginal rays while preserving the back focus distance needed for filter placement
3Adaptability or versatility
If asymmetrical lens alignment is used to achieve wide angle, then viewing angle is improved, but optical performance balance deteriorates
Solution Approach 1:
The patent applies local quality by assigning different optical properties to different parts of the system: the first lens group has negative refractive power with specific curvature characteristics, the second lens group has positive refractive power, and each lens surface has specifically designed curvature radii. This localized optimization of optical properties maintains overall system balance while achieving wide viewing angle
Solution Approach 2:
The patent employs counterweight principle by balancing the negative refractive power of the first lens group with the positive refractive power of the second and third lens groups. This counterbalancing of optical powers compensates for the asymmetrical alignment effects, maintaining optical performance reliability while enabling wide angle capability
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 system effectively corrects aberrations like distortion, astigmatism, and chromatic aberrations, achieving a wide viewing angle of about 30 degrees with minimal distortion of 2%, suitable for camera applications like monitoring and vehicle-mounted cameras, while maintaining a compact size and high imaging performance.
Implementation Method 1
a first lens group with a positive refractive power, an aperture stop, and a second lens group with a positive refractive power. The first lens group includes, in order form the object side, a first front lens group with a negative refractive power and a first rear lens group with a positive refractive power
Data Source
AI summary
A single focal imaging optical system includes, in order from an object side, a first lens group with a positive power, an aperture stop, and a second lens group with a positive power. The first lens group includes a first front lens group and a first rear lens group. The first front lens group includes a negative lens having a concave surface on an image side and a positive meniscus lens having a concave surface on the object side. The first rear lens group includes a biconvex lens. The second lens group includes a second front lens group with a negative power and a second rear lens group with a positive power. The system satisfies a following condition: 3.2<f2/f1<9.0, where f1 represents a composite focal length of the first lens group and f2 represents a composite focal length of the second lens group.