Endoscopic Objective Optical System Aberration Control
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Solution Overview
Problem
Endoscopic objective optical systems face challenges in maintaining low aberration variations during focusing due to insufficient back focus and manufacturing errors, which affect image quality and lead to issues like side blur and astigmatic aberrations.
Innovation Solution
The system comprises a front group with negative refractive power and a rear group with positive refractive power, fixed on an optical axis, satisfying specific conditional expressions to reduce aberration variations and allow placement of optical members like a polarizing prism, while maintaining sufficient refractive power for a wider angle of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the back focus is increased to allow placement of optical members such as a prism, then the adaptability of the system is improved, but the lens size and complexity increase
Solution Approach 1:
The objective optical system is divided into multiple lens groups (first through fourth lens groups) with specific refractive power configurations. This segmentation allows the back focus to be extended to accommodate optical members like prisms while maintaining overall system compactness through optimized group arrangements and individual lens element designs.
2Speed
If the refractive power of the focusing lens is increased to improve focusing capability, then the focusing speed is improved, but the manufacturing precision requirements increase due to larger decentering effects
Solution Approach 1:
The focusing lens is designed with specific local optical properties including a positive meniscus shape with the convex surface facing the object side, and is positioned within a controlled back focus distance range (0.05 ≤ back focus/focal length of focusing lens ≤ 0.15). This local optimization allows sufficient focusing power while reducing sensitivity to decentering errors.
Solution Approach 2:
The patent specifies precise parameter ranges for the focusing lens including its focal length relative to the back focus (0.05 ≤ back focus/focal length of focusing lens ≤ 0.15) and its refractive power relative to the entire system (0.1 ≤ focal length of entire system/focal length of focusing lens ≤ 0.3). These parameter constraints optimize the balance between focusing capability and manufacturing tolerance.
3Area of stationary object
If the refractive power of the front group is increased to achieve a wider angle of view, then the field of view is improved, but the aberration variations during focusing increase
Solution Approach 1:
The front group is segmented into a first lens group with negative refractive power and a second lens group with positive refractive power. This segmentation allows the front group to achieve wide angle of view through the negative power first lens group while the positive power second lens group compensates for aberrations, maintaining aberration consistency during focusing operations.
4Reliability
If the back focus is extended to reduce aberration variations, then the image quality is improved, but the lens size increases
Solution Approach 1:
The patent establishes a specific parameter range for the back focus relative to the focal length of the focusing lens (0.05 ≤ back focus/focal length of focusing lens ≤ 0.15). This parameter optimization allows the back focus to be extended sufficiently to reduce aberration variations during focusing while preventing excessive increase in overall lens size through coordinated design of other lens parameters.
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 suppresses aberrations due to manufacturing errors and focusing, reduces side blur, and prevents image surface inclination, ensuring high-quality images by maintaining refractive power and back focus while keeping lens size in a desired range.
Implementation Method 1
an endoscopic objective optical system includes, in order from an object side to an image side, a front group provided with negative refractive power, a focusing lens, and a rear group provided with positive refractive power
Data Source
AI summary
To allow placement of optical members by providing a long back focus, make aberrations less subject to manufacturing errors, and reduce variations in aberrations during focusing. An endoscopic objective optical system includes, in order from an object side, a front group with negative refractive power, a focusing lens, and a rear group with positive refractive power, wherein: the endoscopic objective optical system satisfies conditional expressions (1) to (4) below:4<FB/FL (1)FL/|fc|<0.1 (2)−3<F_F/FL<−0.9 (3)2.5<F_R/FL<5 (4)where FB is back focus of the entire system, FL is a focal length of the entire system, fc is a focal length of the focusing lens, |fc| is an absolute value of fc, F_F is a focal length of the front group, and F_R is a focal length of the rear group.