Variable Aperture Endoscope for Resolution and Depth of Field Trade-off
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Solution Overview
Problem
Endoscopes face limitations in resolution and depth of field due to the diffraction limit and geometrical optical aberrations, making it challenging to achieve high resolution while maintaining sufficient depth of field for various medical applications.
Innovation Solution
A modular endoscopic imaging system with a variable aperture stop and movable lens elements or lens groups, allowing for adjustment of the aperture and focus to optimize image quality based on the surgical situation, either mechanically or electronically, to balance resolution and depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the aperture stop is increased to reduce the diffraction limit and improve resolution, then the resolution is improved, but the depth of field decreases
Solution Approach 1:
The patent implements a variable aperture stop that can dynamically adjust its opening size based on imaging requirements. The aperture stop transitions from a fixed size to a dynamically adjustable component, allowing the system to optimize between resolution and depth of field by changing the aperture diameter according to the specific medical application needs.
Solution Approach 2:
The patent changes the physical parameter of the aperture stop diameter to resolve the contradiction. By adjusting the aperture diameter parameter, the system can control both the diffraction limit (affecting resolution) and the depth of field, allowing optimization for different imaging scenarios such as overview versus detailed inspection.
2Device complexity
If a fixed focus optical system is used, then the device complexity is reduced, but the image quality for objects at different distances deteriorates
Solution Approach 1:
The patent introduces movable lens elements that can change their position along the optical axis dynamically. This allows the optical system to adjust focus for objects at different distances, transforming a fixed-focus system into an adjustable-focus system that maintains image sharpness across varying object distances without significantly increasing complexity.
Solution Approach 2:
The optical system is divided into multiple lens groups with independent adjustability. Rather than a single fixed lens, the system uses segmented lens elements that can be moved independently or in combination, allowing flexible focus adjustment while maintaining manageable system complexity.
3Reliability
If the aperture stop is decreased to increase the depth of field, then the depth of field is improved, but the resolution decreases due to increased diffraction
Solution Approach 1:
The variable aperture stop allows dynamic adjustment between small and large openings. When overview imaging is required, the aperture can be closed down to increase depth of field. When detailed inspection is needed, the aperture can be opened to maximize resolution, providing optimal performance for each specific medical application.
Solution Approach 2:
The system adjusts the aperture diameter parameter to change the balance between depth of field and resolution. By varying this parameter, the optical system can be optimized for different imaging scenarios, switching between depth-of-field-limited and diffraction-limited operation as needed.
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
Enables high-resolution imaging with adjustable depth of field, allowing for optimal image quality in different medical situations, improving the usability of endoscopes for both overview and detailed inspections within the body cavity.
Implementation Method 1
Based on the so-called diffraction limit of an optical system, the image of an object point imaged through an optical system cannot be a point. The image is a spot of a certain diameter in the image plane. This spot is called the airy disk.
Implementation Method 2
The second limitation of optical instruments is geometrical optical aberrations. Geometrical optical aberrations cannot be avoided when the image of an extended object field is formed by an optical system like an endoscope.
Data Source
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AI summary
Optical systems for flexible and rigid endoscopes that have a low diffraction limit and small geometrical optical aberrations, the systems including an aperture stop where the diameter can be adjusted to select either higher resolution or higher depth of field. The optical systems can include a lens group either to focus on different object distances or on a fixed average object distance. The aperture stop can be adjusted to increase either depth of field or resolution dependent on the endoscopic and surgical situation. Simple symbols help the surgeon to adjust the aperture stop to these situations. The surgeon can either look around the body cavity with large depth of field but moderate overall resolution or focus on a small area with less depth of field but greater resolution. The balance between resolution and depth of field can be adjusted by an automatic image control. Fields in the image field are defined and software used in the camera controller analyzes the sharpness of the different fields. The center field is used to hold or define the sharpness of the image in the center field. Measurements of the sharpness in the peripheral fields define if more depth of field is needed or the resolution can be increased.