Objective Optical System Focusing with Minimal Angle-of-View Change
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Solution Overview
Problem
Conventional endoscopic objective lenses lack focusing functionality, which is necessary for maintaining image quality and viewing depth as high-pixel CCDs are used, leading to a need for lenses with focusing capabilities that minimize angle-of-view changes and ensure wide-angle viewing.
Innovation Solution
An objective optical system comprising a first negative power group, a second positive power group that moves for focusing, and a third positive power group, with specific conditions ensuring minimal angle-of-view changes and compatibility with high-pixel imaging devices, including a positive meniscus lens and cemented lenses to reduce image plane fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-pixel CCDs are used to improve image quality, then image quality is improved, but the F-number must be reduced which leads to narrower viewing depth
Solution Approach 1:
The patent applies dynamics by making the second lens group movable along the optical axis. This movement enables the lens to adjust focus dynamically, allowing the system to maintain both high image quality and extended viewing depth by compensating for the reduced viewing depth caused by using high-pixel CCDs with reduced F-numbers
2Adaptability or versatility
If focusing function is added to maintain viewing depth, then viewing depth is improved, but angle-of-view changes occur during focusing
Solution Approach 1:
The patent applies local quality by assigning specific roles to different lens groups: the first and third lens groups remain fixed to maintain overall optical stability and angle-of-view, while only the second lens group moves to provide focusing. This localized movement minimizes angle-of-view changes during focusing while still achieving the required viewing depth extension
3Reliability
If multiple lens groups are used to achieve focusing with minimal angle-of-view change, then focusing performance is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the lens system into three distinct lens groups with specific power distributions (first group: negative power, second group: positive power, third group: positive power). This segmentation allows the moving second group to handle focusing while the fixed first and third groups maintain optical stability, achieving good focusing performance with controlled complexity
Solution Approach 2:
The patent applies multi-functionality by designing the second lens group to serve multiple purposes: it provides the focusing function through its movement and also contributes to correcting optical aberrations. The fixed first and third lens groups simultaneously provide structural support and maintain the overall optical power distribution, reducing the need for additional corrective elements
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 system enables effective focusing with minimal angle-of-view changes, maintaining high image quality and wide-angle viewing, compatible with high-pixel imaging devices, and reduces the complexity of the mechanical structure.
Implementation Method 1
focusing can be implemented with respect to an object point distance change by movement of the second group
Implementation Method 2
an objective optical system provided, which comprises, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power
Data Source
AI summary
The invention provides a high-performance objective lens that is capable of implementing focusing relative to an object point distance change with no or little angle-of-view change, and is well compatible with a high-pixel type imaging device. The objective optical system comprises, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power. Only the second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (1)-1, (1)-2 and (8):ωf>60 (1)-1ωn>60 (1)-2−1.2<f1/ff<−0.6 (8)whereωf is a maximum half angle of view (°) upon viewing at a far distance object point,ωn is a maximum half angle of view (°) upon close-up viewing,f1 is a focal length of the first lens group, andff is a focal length of the whole system upon viewing at a far distance. See FIG. 1.