Endoscope Objective Optical System Focusing Control
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Solution Overview
Problem
Endoscope objective optical systems face challenges in maintaining image quality and observation depth while reducing size, as lowering the F-number narrows the observation depth and increases the angle of view fluctuation during focusing, making it difficult to transition between normal and close observation modes effectively.
Innovation Solution
The endoscope optical system is designed with a configuration of a first group with negative refractive power, a second group with positive refractive power that moves for focusing, and a third group with positive refractive power, satisfying specific conditional expressions to control the focal lengths and movement distances, thereby minimizing angle of view fluctuations and maintaining operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the F-number is reduced to maintain image quality with high-pixel-count imaging devices, then image quality is improved, but observation depth is narrowed
Solution Approach 1:
The patent implements a focusing mechanism that moves the second lens group (G2) along the optical axis to dynamically adjust the observation depth. By making the optical system dynamic rather than static, the system can adapt between wide observation depth (normal state) and focused observation (close state) while maintaining the reduced F-number for high-pixel-count imaging quality
Solution Approach 2:
The patent changes the focal length parameter of the second lens group (G2) by moving it along the optical axis. This parameter change enables the system to switch between different observation states (normal and close) while maintaining the reduced F-number, thus resolving the contradiction between image quality and observation depth
2Measurement precision
If the F-number is reduced to prevent diffraction degradation, then image quality is improved, but angle of view fluctuation increases during focusing
Solution Approach 1:
The patent assigns different refractive power characteristics to different lens groups: the first group (G1) has negative refractive power while the second group (G2) has positive refractive power. This local differentiation of optical properties allows the system to compensate for angle of view fluctuations during focusing while maintaining the reduced F-number for high image quality
Solution Approach 2:
The second lens group (G2) acts as an intermediary element that, when moved along the optical axis, enables focusing while the combined action of G1 and G2 with their contrasting refractive powers minimizes angle of view fluctuation. This intermediary mechanism resolves the contradiction between maintaining reduced F-number and stabilizing angle of view
3Length of moving object
If the optical system length is reduced to minimize burden on patients, then endoscope size is reduced, but focusing performance deteriorates
Solution Approach 1:
The patent divides the optical system into three separate lens groups (G1, G2, G3) with different refractive power characteristics. This segmentation allows the second group (G2) to be moved independently for focusing while keeping the overall system compact. The divided structure enables effective focusing performance within a reduced endoscope size suitable for patient comfort
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 allows for smooth focusing between normal and close observation states with reduced observation depth variation and improved focus adjustment, ensuring effective image quality and usability of the endoscope without increasing the optical system's length.
Implementation Method 1
a second group (G2) having positive refractive power, and a third group (G3) having positive refractive power in this order from the object side, the second group (G2) moves in an optical-axis direction to perform focusing
Data Source
AI summary
Provided is an endoscope objective optical system including, in order from an object side, a first group having negative refractive power, a second group having positive refractive power, and a third group having positive refractive power. The second group is provided so as to be movable in an optical-axis direction. The following conditional expression is satisfied,9<f2/fa<16 (1)where f2 is a focal length of the second group, and fa is a focal length of the entire system in the normal observation state.