Endoscope Objective Optical System with Prism Nesting
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Solution Overview
Problem
Existing endoscope objective optical systems face challenges in achieving a small size and wide angle of view while maintaining superior image quality, particularly for oblique viewing, due to limitations in the space required for visual-field direction converting members and the correction of aberrations such as spherical and chromatic aberrations.
Innovation Solution
The endoscope objective optical system is designed with a specific configuration including a first group with a negative refractive power and an aperture stop, and a second group with a positive refractive power, incorporating a visual-field direction converting member and cemented lenses to optimize the focal lengths and radii of curvature, satisfying conditional expressions to ensure adequate space for the visual-field direction converting member and appropriate refractive powers for aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a visual-field direction converting member such as a prism is disposed in the optical system for oblique observation, then oblique viewing capability is achieved, but the space required increases making it difficult to achieve a compact size
Solution Approach 1:
The patent integrates the visual-field direction converting member (prism) within the existing optical path by positioning it between the first and second lens groups. The prism is nested within the compact optical system structure, utilizing the space between lens groups rather than adding external bulk, thereby achieving oblique viewing capability while maintaining a compact overall size.
Solution Approach 2:
The patent achieves oblique viewing by introducing a visual-field direction converting member that redirects light in a different spatial dimension. The prism converts the optical path direction without requiring a proportional increase in the longitudinal or lateral dimensions of the entire optical system, effectively utilizing dimensional optimization to resolve the space constraint.
2Volume of moving object
If the optical system is made compact with limited space, then a small size is achieved, but adequate space for the visual-field direction converting member is insufficient
Solution Approach 1:
The patent employs a movable first lens group that can shift along the optical axis. This dynamic positioning capability allows the optical system to adjust the spacing between lens groups, creating adequate space for the visual-field direction converting member when needed while maintaining a compact form when the conversion function is not actively required. The conditional expressions ensure proper spacing under various operational states.
3Adaptability or versatility
If lens configurations are optimized for wide angle of view, then wide angle capability is achieved, but aberration correction becomes more difficult
Solution Approach 1:
The patent uses a cemented lens in the second group comprising lenses with different refractive indices and Abbe numbers. This composite lens structure allows simultaneous correction of spherical aberration and chromatic aberration. The conditional expressions on focal lengths and radii of curvature are specifically designed to balance wide angle capability with aberration correction, using the composite lens to reconcile the trade-off between these parameters.
Solution Approach 2:
The patent assigns specific optical properties to different lens groups: the first group has negative refractive power for wide angle coverage, while the second group has positive refractive power with a cemented lens structure specifically designed for aberration correction. Each lens group is optimized for its local function, with the conditional expressions ensuring that the combination achieves both wide angle capability and superior aberration correction.
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 a compact endoscope with a wide angle of view and superior image quality, effectively addressing the challenges of aberration correction and space constraints for oblique viewing.
Implementation Method 1
a first lens having a negative refractive power
Implementation Method 2
a visual-field direction converting member
Implementation Method 3
a second lens having a biconvex shape
Implementation Method 4
a cemented lens in which a third lens having a positive refractive power and a fourth lens having a negative refractive power are cemented
Data Source
AI summary
There is provided an endoscope objective optical system with a small size and a high image quality, and in which, an adequate space for disposing a visual-field direction converting element is secured. The endoscope objective optical system, comprising in order from an object side:a first group having a negative refractive power;an aperture stop; anda second group having a positive refractive power, whereinthe first group includes in order from the object side, a first lens having a negative refractive power and a visual-field direction converting member, andthe second group includes in order from the object side, a second lens having a biconvex shape and a cemented lens in which a third lens having a positive refractive power and a fourth lens having a negative refractive power are cemented in this order, andthe endoscope objective optical system satisfies the following conditional expressions (1), (2), (3), and (4)2.4≦d1/f≦4.6 (1)1.85≦f2/f≦2.6 (2)−50≦r21/r22≦−0.4 (3)2.01≦f03/f≦2.5 (4)where,d1 denotes an air conversion length from a surface on an image side of the first lens up to a surface of the aperture stop,f denotes a focal length of the overall endoscope objective optical system,f2 denotes a focal length of the second group,r21 denotes a radius of curvature of a surface on the object side of the second lens,r22 denotes a radius of curvature of a surface on the image side of the second lens, andf03 denotes a focal length of the third lens.