Endoscope Objective Optical System with Intermediate Image Relay
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Solution Overview
Problem
Existing endoscope objective optical systems face challenges in achieving a wide angle of view with a small effective luminous flux diameter on the lens surface closest to the object while maintaining good optical performance, due to limitations in lens size and illumination light distribution, and the need for a cover glass that contradicts size reduction demands.
Innovation Solution
The objective optical system forms an intermediate image at a position conjugate to the object surface and on an imaging plane, satisfying specific conditional expressions to achieve a wide angle, small effective luminous flux diameter, and good optical performance, including the use of a plane-parallel plate closer to the object than the lens surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the effective luminous flux diameter on the lens surface closest to the object is increased to correct wide angle aberration, then the optical performance is improved, but the lens diameter is increased
Solution Approach 1:
The optical system is divided into multiple lens groups with different functions. The first lens group (closer to object) and second lens group (closer to image) are segmented to separately handle aberration correction and light gathering, allowing the front lens diameter to be reduced while maintaining overall optical performance through coordinated design of both groups
Solution Approach 2:
The patent introduces a relay magnification dimension (βR) and intermediate image formation to transform the optical path geometry. By forming an intermediate image and using a relay system with specific magnification range (−0.5 < βR < 0), the system achieves wide angle coverage and aberration correction without requiring a large front lens diameter
2Area of stationary object
If the lens diameter is reduced to simplify illumination system disposition, then the endoscope size is reduced, but the illumination light distribution in proximity area is affected
Solution Approach 1:
The patent introduces a plane-parallel plate as an intermediary optical element between the lens and the object. This plate serves as a mediator that maintains the optical path and illumination characteristics while allowing the use of a smaller lens diameter, thereby preserving proximity area illumination without requiring a large lens
3Ease of manufacture
If a cover glass is disposed on the lens surface closest to the object to simplify sterilization and repair, then the ease of manufacture is improved, but the endoscope size increases
Solution Approach 1:
Instead of placing the cover glass on the traditional front lens surface (which would require a large diameter), the patent inverts the approach by positioning the cover glass on a different surface in the optical path where a smaller diameter is sufficient. This allows sterilization and repair benefits while maintaining a compact endoscope size
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 reduced lens diameter, corrected aberration, and sufficient illumination, ensuring a wide angle of view and enabling the placement of an illumination optical system, while also simplifying sterilization and repair measures by reducing the endoscope's size.
Implementation Method 1
further comprises a plane-parallel plate provided to be closer to the object than the lens surface closest to the object
Implementation Method 2
An objective optical system for an endoscope of the invention forms an intermediate image at a position conjugate to an object surface and forms the intermediate image on an imaging plane again
Data Source
AI summary
An objective optical system for an endoscope forms an intermediate image at a position conjugate to an object surface and forms the intermediate image on an imaging plane again, and is adapted to satisfy Conditional expressions (1) to (3) in a case in which a maximum effective image height on the imaging plane is denoted by HI, a focal length of the entire system is denoted by f, an effective luminous flux diameter on a lens surface closest to an object is denoted by FD, an F-Number of the entire system is denoted by FNo, and a paraxial relay magnification of the intermediate image on the imaging plane is denoted by R.0.7<HI/|f| (1)FD×FNo/|f|6 (2)−2<βR<−0.8 (3).