Endoscope Objective Lens with Variable Focal Length and Wide Angle of View
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Solution Overview
Problem
Existing endoscope objective lenses lack the ability to seamlessly switch between focusing on objects at far and near points while maintaining a large depth of field and good optical performance, particularly in near point-object-observation states, leading to user overload and prolonged diagnostic times.
Innovation Solution
The development of an objective lens for endoscopes that includes a stop, concave surface lenses on the object side, and cemented lenses on the image side, allowing for movement of some lenses along the optical axis to switch between far and near point focusing, with specific conditional expressions ensuring a total angle of view of 120° or more and optimal F-number ratios, thereby enhancing depth of field and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the focal length is increased to expand the depth of field in near point observation, then the depth of field increases, but the angle of view decreases and image contrast deteriorates
Solution Approach 1:
The objective lens is divided into multiple lens groups with different functions: a first lens group with negative refractive power, a second lens group with positive refractive power, and a third lens group with negative refractive power. Each group contributes differently to focal length adjustment and depth of field control, allowing independent optimization of depth of field and angle of view without requiring a single monolithic lens design.
Solution Approach 2:
Different regions of the optical system are assigned different optical properties. The first lens group has a specific negative refractive power designed for wide-angle performance, the second lens group has positive refractive power for focal length adjustment, and the third lens group has negative refractive power for aberration correction. This local differentiation allows the system to maintain both large angle of view and expanded depth of field simultaneously.
2Reliability
If the focal length is increased to expand the depth of field in near point observation, then the depth of field increases, but the F number increases excessively causing image contrast deterioration
Solution Approach 1:
The optical system dynamically adjusts the F number based on the observation distance. When focusing on near-point objects, the focal length is extended to increase depth of field, and simultaneously the F number is increased to maintain optimal image contrast. This dynamic adjustment allows the system to adapt to different observation conditions, preserving image quality across varying depths of field requirements.
3Device complexity
If a fixed focal length lens is used, then the structure is simple, but the lens cannot switch between far-point and near-point focusing
Solution Approach 1:
The objective lens incorporates a variable focal length mechanism that allows dynamic adjustment between different focal lengths. The lens system can switch between a first focal length optimized for far-point observation and a second focal length optimized for near-point observation. This dynamic capability enables the lens to adapt to different observation distances while maintaining good optical performance in both regimes.
Solution Approach 2:
The objective lens is designed to perform multiple functions: it can focus on both far-point and near-point objects, maintain large depth of field in near-point observation, preserve wide angle of view, and control image contrast through F number adjustment. This multi-functionality is achieved through the coordinated design of multiple lens groups with different refractive powers and the ability to vary focal length and F number based on observation conditions.
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 solution enables the endoscope to maintain a wide field of view and suppress astigmatism, reducing user load and shortening diagnostic times by ensuring a large depth of field in near point-focusing states while preventing excessive focal length increase and image contrast deterioration.
Implementation Method 1
at least one lens which is disposed closer to an object side than the stop and of which an image-side lens surface is a concave surface
Implementation Method 2
at least one set of cemented lenses that is disposed closer to an image side than the stop
Data Source
AI summary
The objective lens for an endoscope includes a stop, at least one lens which is disposed closer to an object side than the stop and of which an image-side lens surface is a concave surface, and at least one set of cemented lenses that is disposed closer to an image side than the stop; focusing on an object positioned at a nearest point from an object positioned at a farthest point is performed by movement of some lenses of an entire system along an optical axis; the objective lens for an endoscope has a total angle of view of 120° or more in a state where focusing on the object positioned at the farthest point is performed and in a state where focusing on the object positioned at the nearest point is performed; and the objective lens for an endoscope satisfies predetermined conditional expressions.