Compact Imaging Optical System for Endoscopes
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Solution Overview
Problem
Existing wide angle imaging optical systems for endoscopes and mobile devices are too large in diameter and length, limiting their use in compact applications such as nasal endoscopes and mobile phones, and struggle with aberrations like chromatic aberration.
Innovation Solution
A compact imaging optical system with a negative first lens group, a positive second lens group, a positive third lens group, and a negative fourth lens group, arranged symmetrically about an aperture stop, which satisfies specific expressions to reduce total length and outer diameter while correcting chromatic aberration and other optical aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the outer diameter of the imaging optical system is reduced to fit compact devices, then the device can be incorporated in mobile terminals and endoscopes, but the image quality deteriorates due to uncorrected aberrations
Solution Approach 1:
The patent applies parameter changes by carefully selecting and optimizing the refractive indices and Abbe numbers of the lens materials. Specifically, it uses a first lens with high refractive index (1.7-1.9) and low Abbe number (20-30) to control chromatic aberration, while the second lens has complementary parameters (refractive index 1.4-1.6, Abbe number 30-50). This parameter optimization allows the system to achieve compact dimensions while maintaining image quality through effective aberration correction.
Solution Approach 2:
The patent employs composite materials by combining multiple lens elements with different material properties in a single optical system. The first lens uses high-refractive-index glass (n=1.7-1.9) while the second lens uses lower-refractive-index glass (n=1.4-1.6), creating a composite optical structure that corrects chromatic aberration. This material combination allows the system to achieve both compact size and high image quality.
2Length of stationary object
If the total length of the imaging optical system is reduced to shorten the rigid tip section, then the physical stress on patients is reduced, but the optical performance deteriorates due to increased aberrations
Solution Approach 1:
The patent uses parameter changes by optimizing the focal lengths and曲率 radii of the lens surfaces. The first lens has focal length f1 and the second lens has focal length f2, with specific relationships between these parameters and the image height h. By controlling the ratio f1/h and f2/h within specific ranges, the system achieves compact total length while maintaining optical performance through effective aberration correction.
Solution Approach 2:
The patent applies segmentation by dividing the imaging optical system into multiple lens groups (first lens and second lens) with distinct functions. The first lens primarily handles chromatic aberration correction while the second lens contributes to overall focal length and image quality. This segmentation allows each lens to be optimized independently for specific aberration correction, achieving compact total length without sacrificing optical performance.
3Area of stationary object
If the diameter of the lens proximate to the object or image plane is reduced to decrease the outer diameter, then the imaging optical system fits compact devices, but chromatic aberration increases
Solution Approach 1:
The patent applies parameter changes by selecting specific refractive indices and Abbe numbers for the lens materials. The first lens uses high refractive index (1.7-1.9) and low Abbe number (20-30) to strongly control chromatic aberration, while the second lens has complementary parameters (refractive index 1.4-1.6, Abbe number 30-50). This parameter optimization allows the system to achieve compact dimensions while maintaining image quality through effective aberration correction.
Solution Approach 2:
The patent employs composite materials by combining multiple lens elements with different material properties in a single optical system. The first lens uses high-refractive-index glass (n=1.7-1.9) while the second lens uses lower-refractive-index glass (n=1.4-1.6), creating a composite optical structure that corrects chromatic aberration. This material combination allows the system to achieve both compact size and high image quality.
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 achieves a significantly reduced outer diameter and total length of the imaging optical system, enabling high-quality imaging with wide field angles while effectively correcting various aberrations, making it suitable for compact devices like endoscopes and mobile phones.
Implementation Method 1
a negative first lens group, a positive second lens group, a positive third lens group, and a negative fourth lens group
Data Source
AI summary
An imaging optical system comprises a first lens group composed of a negative single lens, a second lens group composed of a positive lens element and a negative lens element attached together, an aperture stop, a third lens group composed of a positive lens element and a negative lens element attached together, and a fourth lens group composed of a negative single lens, in this order from an object side. Expressions 0.37<hF/IH<0.5 and 0.37<hR/IH<0.5 are satisfied where “IH” denotes a maximum image height on an image plane, “hF” denotes an incident height of a principal ray, directed to a position of the maximum image height on the image plane, at its entrance into the first lens group, and “hR” denotes an exit height of the principal ray at its exit from the fourth lens group.