Wide-Angle Objective Optical System Using Aspheric Resin Lenses
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Solution Overview
Problem
Existing objective optical systems for endoscopes face challenges in achieving both wide-angle views and sufficient aberration correction while minimizing size and cost, particularly when using low-refractive-index materials like resin, which complicates the design and increases the complexity of lens arrangement.
Innovation Solution
The objective optical system is designed with a negative-powered first group, a positive-powered second group with an aspheric surface, and a third group with a convex surface on the object side, where the distance between the second and third groups is shorter than the distance between the first and second groups, optimizing lens placement and material usage to achieve a wide angle of view and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the number of lenses is reduced to lower cost, then manufacturing cost is reduced, but aberration correction becomes insufficient
Solution Approach 1:
The patent changes the optical parameters by introducing aspheric surfaces on specific lens surfaces (object-side surface of the second lens and image-side surface of the third lens) and carefully controlling focal lengths and spacing between lens groups. This allows a reduced three-lens configuration to achieve sufficient aberration correction while maintaining low manufacturing cost
Solution Approach 2:
The patent combines different material types (resin and glass) strategically - using resin for the first and second lenses where aspheric surfaces provide cost-effective aberration correction, and glass for the third lens where high precision is needed. This composite material approach optimizes both cost and optical performance
2Adaptability or versatility
If the angle of view is widened to 130 degrees or more, then field of view is improved, but aberration correction becomes more difficult
Solution Approach 1:
The patent divides the optical system into three functional groups with distinct roles: the first lens (negative power) handles wide-angle light gathering, the second lens (positive power with aspheric surface) provides primary aberration correction, and the third lens (positive power) fine-tunes the optical path. This segmentation allows each component to be optimized for its specific function while achieving overall wide-angle performance with sufficient aberration correction
Solution Approach 2:
The patent applies aspheric surfaces to the object-side surface of the second lens and the image-side surface of the third lens. These curved surfaces are specifically designed to correct spherical aberration and other off-axis aberrations that become more severe at wide angles, enabling 130-degree or greater field of view while maintaining image quality
3Length of moving object
If the entire length is reduced for miniaturization, then device size is reduced, but optical performance deteriorates
Solution Approach 1:
The patent employs a compact nested arrangement where the three lens groups are tightly integrated along the optical axis with minimized spacing. The conditional expression 0.3 < d23/d12 < 1.0 ensures that the distance between the second and third lenses (d23) is appropriately related to the distance between the first and second lenses (d12), creating a space-efficient configuration that maintains optical performance while achieving miniaturization
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: the focal lengths of individual lenses, the spacing between lens groups (particularly the ratio d23/d12), and the application of aspheric surfaces. These parameter changes enable the system to achieve short overall length without sacrificing optical performance, as the aspheric surfaces compensate for the reduced margin for error in a compact design
4Ease of manufacture
If low-cost resin materials with lower refractive indices are used, then manufacturing cost is reduced, but achieving wide angle of view and size reduction becomes more difficult
Solution Approach 1:
The patent compensates for the lower refractive index of resin materials by optimizing other parameters: using negative power for the first lens to expand the field of view, applying aspheric surfaces to the second and third lenses to correct aberrations, and carefully controlling the spacing ratio d23/d12. These parameter changes allow low-cost resin materials to achieve 130-degree or greater angle of view and compact size
Solution Approach 2:
The patent uses a composite material strategy where resin (low-cost, lower refractive index) is used for the first and second lenses where aspheric surfaces provide effective aberration correction, and glass (higher cost, higher refractive index) is used for the third lens where precise optical control is needed. This composite approach balances cost and 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 enables a wide-angle objective optical system with an angle of view of 130 degrees or more, while minimizing the overall length and cost, using low-refractive-index materials like resin, and maintaining effective aberration correction and optical performance.
Implementation Method 1
a surface of the second group which is closest to the image side is an aspheric surface
Implementation Method 2
a surface of the third group which is closest to the object side is a convex surface
Data Source
Figure 1A~1B
Figure 1C
Figure 2A~2B
AI summary
An objective optical system includes, in order from an object side, a negative-powered first lens (L1), a lens stop (S), a positive-powered second lens (L2), and a third lens (L3), wherein: a surface (2) of the first lens (L1) which is closest to an image side is a concave surface; a surface (6) of the second lens (L2) which is closest to the image side is an aspheric surface; a surface (7) of the third lens (L3) which is closest to the object side is a convex surface; a distance d_L23 between the second lens (L2) and the third lens (L3) is smaller than a distance d_L12 between the first lens (L1) and the second lens (L2), satisfying a conditional expression d_L23/d_L12 <0.25.