Objective Optical System for Endoscope Miniaturization
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Solution Overview
Problem
There is a demand for further miniaturization of endoscopes with large angles of view without compromising optical performance, particularly in reducing the dimensions of lenses and optical members beyond the aperture stop while maintaining or improving the angle of view and avoiding increased aberrations.
Innovation Solution
The objective optical system consists of a first lens group with negative refractive power and a second lens group with positive refractive power, including specific configurations of cemented lenses and single lenses, which satisfy certain focal length conditions to minimize the outer diameters and heights of lenses while maintaining optical performance, allowing for a wider angle of view and reduced dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the dimensions of lenses and optical members beyond the aperture stop are decreased to miniaturize the endoscope, then the size of the endoscope is reduced, but the angle of view may decrease and aberrations may increase
Solution Approach 1:
The patent applies parameter changes by optimizing the focal length ratios of specific lens groups. Conditional Formula (1) controls the ratio between the focal length of the first lens group (f1) and the second lens group (f2) to maintain a wide angle of view while reducing overall size. Conditional Formula (2) controls the ratio between the focal length of the negative lens (f(RN)) and the second lens group (f2) to suppress field curvature and aberrations during miniaturization. These parameter optimizations enable the endoscope to achieve compact dimensions without sacrificing optical performance.
2Volume of moving object
If the outer diameters of cemented lenses beyond the aperture stop are decreased to reduce size, then the endoscope is miniaturized, but optical performance may deteriorate
Solution Approach 1:
The patent uses parameter changes to optimize the focal length ratio f(RN)/f2, where f(RN) is the focal length of the negative lens in the cemented lens and f2 is the focal length of the second lens group. By controlling this parameter within a specific range defined by Conditional Formula (2), the design achieves miniaturization of the cemented lens outer diameter while suppressing field curvature and maintaining aberration correction performance.
3Volume of moving object
If single lenses are used instead of cemented lenses to reduce dimensions, then the optical system is simplified and size is reduced, but lateral chromatic aberrations may increase
Solution Approach 1:
The patent applies composite materials by using cemented lenses composed of multiple lens materials with different refractive indices and Abbe numbers. The first lens group includes a cemented lens formed by cementing a positive lens and a negative lens made of different materials, and the second lens group similarly uses a cemented lens with multiple materials. This composite structure enables effective correction of lateral chromatic aberrations while maintaining compact dimensions, as the different materials compensate for each other's chromatic dispersion characteristics.
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 the miniaturization of endoscopes by reducing the outer diameters of cemented lenses and the heights of light rays without decreasing optical performance, achieving a wider angle of view and suppressing field curvature, thus facilitating the placement of additional optical members.
Implementation Method 1
an objective optical system includes a first lens group having a negative refractive power, an aperture stop, and a second lens group having a positive refractive power, in this order from an object side
Data Source
AI summary
An objective optical system includes: a negative first lens group; an aperture stop; and a positive second lens group, provided in this order from an object side. The first lens group includes a first lens, which is a negative single lens, and a cemented lens formed by cementing a positive lens and a negative lens together, provided in this order from the object side. The second lens group includes a fourth lens, which is a positive single lens, and a cemented lens formed by cementing a positive lens and a negative lens together, provided in this order from the object side. The objective optical system satisfies Conditional Formula (1): f1/f<1.1, wherein f1 is the focal length of the lens provided most toward the object side, and f is the focal length of the entire lens system.