Endoscope Objective Lens System Compact Chromatic Aberration Correction
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Solution Overview
Problem
Conventional objective lens systems for endoscopes with cemented lens components close to image surfaces face challenges in correcting chromatic aberrations while maintaining a compact length, as they require large diameters and thicknesses, leading to prolonged optical system lengths and difficulties in independently adjusting lateral and longitudinal chromatic aberrations.
Innovation Solution
The objective lens system comprises a configuration of at least four or five lens elements, including a first negative lens, a second positive lens, an aperture stop, and a cemented lens component, optimized by specific conditions for focal lengths and Abbe's numbers to correct chromatic aberrations efficiently, allowing for independent adjustment of aberration correction and reducing the overall length of the optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cemented lens components are disposed close to image surfaces to correct lateral chromatic aberration, then chromatic aberration correction is improved, but the outside diameter and thickness of the cemented lens components increase, leading to prolonged total length of the optical system
Solution Approach 1:
The patent relocates the cemented lens component from a position close to the image surface to a position closer to the object side, specifically between the stop and the second lens element. This spatial repositioning in the optical path allows the component to correct chromatic aberrations effectively while reducing the overall optical system length, as the corrected rays converge more efficiently before reaching the image plane.
Solution Approach 2:
The patent specifies precise focal length relationships for the lens elements in the cemented component (|f3/f4| between 0.2-0.8 and f3/(f1+f2) between 0.3-0.7) and particular Abbe number ranges (50<ν4<70, 20<ν3<50) to optimize the balance between chromatic aberration correction capability and compact system dimensions, enabling effective correction with reduced component size.
2Measurement precision
If cemented lens components are disposed close to image surfaces, then lateral chromatic aberration is corrected, but spaces must be reserved for adjusting imaging locations, further enlarging total lengths
Solution Approach 1:
By repositioning the cemented lens component to a location between the stop and the second lens element rather than near the image surface, the patent eliminates the need for additional adjustment spaces between the cemented component and the image plane, as the component's new position allows for inherent focus adjustment capability within the lens assembly itself.
Solution Approach 2:
The cemented lens component positioned between the stop and second lens element serves multiple functions simultaneously: correcting lateral chromatic aberration, enabling longitudinal chromatic aberration correction through the specified focal length relationships, and providing inherent imaging location adjustment capability, thereby eliminating the need for separate adjustment mechanisms and spaces.
3Measurement precision
If cemented lens components have large outside diameters to correct lateral chromatic aberration, then correction effectiveness is improved, but the components must be thicker to reserve sufficient edge thickness
Solution Approach 1:
The patent specifies that the Abbe number of the positive lens element (ν4) should be between 50 and 70, and the Abbe number of the negative lens element (ν3) should be between 20 and 50, with specific focal length ratios. These parameter constraints enable effective lateral chromatic aberration correction with optimized lens curvatures and thicknesses, avoiding excessive edge thickness requirements.
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 effectively corrects lateral and longitudinal chromatic aberrations while maintaining a compact optical system length, improving image quality and simplifying the lens barrel composition by optimizing ray incidence angles on the image pickup device.
Implementation Method 1
a cemented lens component consisting of a third negative lens element and a fourth positive lens element... to correct lateral chromatic aberration and longitudinal chromatic aberration produced by other lens elements
Implementation Method 2
an objective lens system which consists of a first negative lens element, a second positive lens element, an aperture stop, and a cemented lens component
Data Source
AI summary
An objective lens system for endoscope comprising at least a first negative lens element, a second positive lens element, an aperture stop, and a cemented lens component consisting of a third negative lens element and a fourth positive lens element, and being configured so as to satisfy the conditions (2), (5) and (4) or the conditions (2), (3) and (4) which are mentioned below, whereby the lens system corrects lateral chromatic aberration and longitudinal chromatic aberration with a good balance, favorably corrects aberrations such as chromatic aberration and has a compact composition or a short total length. D2/f<0.9 (2) |f/(f1×&ngr;1)+f/(f2×&ngr;2)|<0.025 (5) 1.5<|(f4×&ngr;1)/(f3×&ngr;3)| (4) |f/(f5×&ngr;5)−f/(f1×&ngr;1)−f/(f2×&ngr;2)|<0.025. (3)