Objective Optical System for Endoscope with Movable Lens Group
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Solution Overview
Problem
Conventional endoscope objective lenses face challenges in achieving high image quality and magnified observation due to a narrow depth of field and limited focusing capabilities, especially when transitioning between normal and magnified observation modes.
Innovation Solution
An objective optical system comprising a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, where focusing is achieved by moving the second lens group, and the third lens group includes a positive lens and a cemented lens with a positive and negative lens configuration, satisfying specific conditional expressions to optimize focal length and air space arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixels is made large to achieve high image quality, then the pixel area becomes small, but the point image size does not reduce accordingly leading to degraded image quality
Solution Approach 1:
The patent changes the F-number parameter from conventional values to a specific range (F1.8 to F3.5) to optimize the balance between pixel size and point image size. By controlling the F-number within this range, the system ensures that the point image size matches the reduced pixel area in high-definition image pickup elements, thereby maintaining high image quality without requiring smaller pixels alone.
2Manufacturing precision
If the F-number is made small to reduce point image size, then the depth of field becomes narrow, but this limits the focusing range
Solution Approach 1:
The patent introduces a movable lens group that can dynamically adjust its position along the optical axis. This dynamic mechanism allows the system to maintain a small F-number for reduced point image size while compensating for the narrow depth of field by shifting the lens position to refocus at different object distances, thereby extending the effective focusing range.
3Area of stationary object
If the focal length is made long to accommodate large image pickup element size, then the depth of field becomes narrow, but this reduces the observation range
Solution Approach 1:
The patent divides the optical system into multiple lens groups with different functions. The first lens group (positive refractive power) and second lens group (negative refractive power) work together to achieve a long focal length for large image pickup elements, while the movable third lens group (positive refractive power) provides focusing adjustment capability. This segmentation allows the system to maintain a long focal length for adequate sensor size while enabling depth of field adjustment through the movable group.
4Measurement precision
If the objective lens is designed for magnified observation with short object distance, then the magnification is improved, but the observation range becomes narrow making it difficult to find lesion parts
Solution Approach 1:
The patent designs the objective optical system to perform multiple functions: it can achieve both magnified observation (for detailed lesion examination) and wide-range observation (for locating lesion parts). The movable lens group enables the system to switch between these modes by adjusting its position, allowing the same optical system to serve both high-magnification diagnostic needs and broad survey capabilities without requiring separate systems.
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 both normal and magnified observations with high image quality and extended magnification, while minimizing aberration fluctuations and simplifying the focusing mechanism, thus addressing the limitations of conventional endoscope lenses.
Implementation Method 1
an objective optical system includes, in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power
Implementation Method 2
focusing is carried out by moving the second lens group
Implementation Method 3
the third lens group includes at least a positive lens and a cemented lens, and the cemented lens in the third lens group includes a positive lens and a negative lens
Data Source
AI summary
The objective optical system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. Focusing is carried out by moving the second lens group. The third lens group includes a positive lens and a cemented lens, and the cemented lens includes a positive lens and a negative lens. A first sub-unit includes a lens positioned on the object side of a predetermined air space and a second sub-lens group includes a lens positioned on an image side of the predetermined air space. The predetermined air space is the maximum air space among the air spaces in the third lens group.