Symmetric Endoscope Objective Lens for Wide-Angle Aberration Control
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Solution Overview
Problem
Endoscope objective lenses face challenges in compensating off-axis aberrations and are sensitive to surface figure errors and positional tolerances due to their compact dimensions and wide-angle optical characteristics, particularly in narrow tortuous lumens requiring deflection exceeding 90°.
Innovation Solution
An endoscope objective lens design featuring a symmetric structure with lenses arranged along the optical axis, including a first and fourth lens with negative optical power and a second and third lens with positive optical power, where the chief ray heights and effective optical diameters of these lenses are balanced to achieve approximate symmetry, reducing aberration correction difficulties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the objective optical system is made compact to reduce the length from the front end to the bending portion, then the observable area within saccular organs is expanded, but the difficulty of compensating off-axis aberration increases and sensitivity to surface figure errors and positional tolerances is heightened
Solution Approach 1:
The patent employs asymmetric lens configurations where specific lenses have different curvature radii on their object-side and image-side surfaces. For example, the first lens has a positive curvature radius on the object-side surface and a negative curvature radius on the image-side surface, creating asymmetric optical paths that help balance aberrations while maintaining compact dimensions. This asymmetric design allows the system to achieve wide-angle imaging (≥120° field of view) with reduced sensitivity to manufacturing tolerances.
Solution Approach 2:
The patent utilizes specific parameter ranges for lens curvature radii, focal lengths, and spacing to optimize the balance between compact size and aberration control. By carefully selecting parameters such as the curvature radii (R1, R2, etc.), focal lengths (f1, f2, etc.), and axial spacings (d1, d2, etc.), the system achieves a compact objective optical system that maintains manufacturing feasibility while correcting off-axis aberrations effectively.
2Area of stationary object
If the field of view is increased to ≥120 degrees to achieve wide-angle imaging, then the observable area is expanded, but the difficulty in compensating off-axis aberration at peripheral fields increases
Solution Approach 1:
The patent divides the optical system into multiple discrete lens components (first lens, second lens, third lens, fourth lens, etc.), each with specific optical powers and surface curvatures. This segmentation allows individual lenses to be optimized for specific functions: some lenses primarily correct spherical aberration, others address coma, and others handle astigmatism. The aperture stop is strategically positioned to control chief ray angles, further aiding in off-axis aberration correction across the wide field of view.
Solution Approach 2:
The patent introduces an aperture stop as an intermediary element that controls the angular distribution of chief rays. By positioning the aperture stop at a specific location within the optical system, it limits the maximum chief ray angle, which directly reduces off-axis aberrations such as coma and distortion. This intermediary element acts as a mediator between the wide field of view requirement and the aberration control requirement, enabling ≥120° imaging while maintaining acceptable image quality across the 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
The symmetric lens configuration effectively compensates for aberrations, improving imaging quality by reducing sensitivity to tolerances and maintaining a wide field of view, suitable for narrow anatomical access.
Implementation Method 1
a first lens having a negative optical power... a second lens having a positive optical power... a third lens having a positive optical power... a fourth lens having a negative optical power
Data Source
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AI summary
The present disclosure relates to the field of endoscopy, specifically to an endoscope objective lens. In the optical system of the objective lens, a first lens, a second lens, an aperture stop, a third lens and a fourth lens are sequentially arranged from the image side to the object side along the optical axis. The first and fourth lenses have negative optical power, while the second and third lens have positive optical power. The chief ray height h11 on the object side surface of the first lens and the chief ray height h42 on the image side surface of the fourth lens satisfy: 0.65 ≤ h11/h42 ≤ 1.35; and/or the effective optical diameter D11 of the object side surface of the first lens and the effective optical diameter D42 of the image side surface of the fourth lens satisfy: 0.75 ≤ D11/D42 ≤ 1.25. This configuration enables approximate symmetry between the first and fourth lens, resulting in approximately symmetric light paths through the two lenses. Consequently, partial mutual cancellation of aberrations occurs, thereby reducing aberration correction difficulty and tolerance sensitivities of optical surfaces.