Endoscope Objective Optical System Compact Design
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Solution Overview
Problem
The challenge in developing an objective optical system for endoscopes is to achieve a small-sized, high-image-quality system with a wide angle of view while minimizing shifts in focus and angle of view due to manufacturing variations, which often result in degraded optical performance and increased costs due to the need for precise adjustments and susceptibility to vignetting and barrel distortion.
Innovation Solution
The system consists of a front group with negative refractive power and a rear group with positive refractive power, including specific lens configurations and cemented lenses, which are arranged to satisfy conditional expressions that optimize focal lengths, lens thicknesses, and refractive powers to reduce shifts and maintain a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the aperture stop is made small-sized to reduce the overall system size, then the system becomes more compact, but the image resolution is degraded due to diffraction effects
Solution Approach 1:
The patent changes the optical parameters by introducing a lens with high refractive power (focal length 0.02mm to 0.08mm) positioned close to the image pickup element. This high refractive power lens compensates for the diffraction effects caused by the small aperture stop, allowing the system to maintain both compact size and high image resolution simultaneously.
2Measurement precision
If a bright optical system with small F-number is used to improve image resolution, then the image quality improves, but aberration correction becomes difficult and depth of field becomes narrow
Solution Approach 1:
The patent segments the optical system into distinct functional groups: a front group with negative refractive power for light gathering, a small aperture stop for controlling light, and a rear group with high refractive power lens for aberration correction and focusing. This segmentation allows each component to be optimized for its specific function while working together to achieve both high resolution and acceptable aberration correction.
3Volume of moving object
If the image height is made small to reduce system size, then the system becomes more compact, but the angle of deviation becomes large and assembly adjustment becomes difficult
Solution Approach 1:
The patent changes the optical parameters by introducing a lens with high refractive power (focal length 0.02mm to 0.08mm) that has a small focal length. This small focal length reduces the lever arm for angular deviations, thereby reducing the angle of deviation effect and making assembly adjustment more tolerant while maintaining a compact image height.
4Area of moving object
If the angle of view is widened to about 160° to improve field coverage, then the field of view increases, but vignetting occurs in the peripheral portion of the image field
Solution Approach 1:
The patent changes the optical parameters by introducing a lens with high refractive power positioned close to the image pickup element. This configuration changes the light path geometry, allowing the system to achieve a wide angle of view (160°) while the high refractive power lens compensates for the vignetting that would otherwise occur in the peripheral portions of the image field.
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 small-sized objective optical system that achieves a wide angle of view and high-definition image quality while suppressing shifts in focus and angle of view, thereby reducing manufacturing errors and maintaining optical performance.
Implementation Method 1
an objective optical system for endoscope which consists of in order from an object side, a front group having a negative refractive power, an aperture stop, and a rear group having a positive refractive power
Data Source
AI summary
An objective optical system for endoscope consists of a front group having a negative refractive power, an aperture stop, and a rear group having a positive refractive power. The front group consists of a first lens having a negative refractive power and a second lens having a positive refractive power. The rear group consists of a third lens having a positive refractive power, a cemented lens of a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power. A shape of the second lens is a meniscus shape having a convex surface directed toward an image side. The sixth lens is cemented to a plane parallel plate, and the following conditional expressions (1) and (2) are satisfied:1.0<f3/d6<2.8 (1)1.7<|f1/f1<10 (2).