Afocal Correction Lens for Dome Window Astigmatism
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Solution Overview
Problem
Optical observation devices with mobile orientation and a dome-shaped window suffer from significant aberration defects, particularly astigmatism, due to the window's curvature and the amplification by relative orientation means like prisms, which degrades image quality and sighting performance, especially in applications like missile guidance.
Innovation Solution
Incorporating optical correction means between the window and relative orientation means to form an afocal optical system, using a lens with equal but opposite optical power to the window, which corrects astigmatism defects immediately after their occurrence, preventing propagation and amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dome-shaped window is used to maintain aerodynamic profile, then aerodynamic performance is improved, but astigmatism aberration is generated due to window curvature
Solution Approach 1:
An optical correction means is introduced as an intermediary element between the dome-shaped window and the observation device. This correction means acts as a mediator that compensates for the astigmatism aberration generated by the curved window, allowing the aerodynamic dome shape to be maintained while restoring optical quality.
Solution Approach 2:
The optical correction means modifies the optical parameters of the light beam by introducing compensating aberrations. Through careful design of the correction means with specific optical power and positioning, the astigmatism induced by the dome window is counterbalanced, transforming the degraded optical state back to an acceptable quality level.
2Adaptability or versatility
If relative orientation means (prisms) are used to enable wide field observation, then field of view is improved, but aberration defects are amplified due to working with divergent beams
Solution Approach 1:
The optical correction means is positioned to act on the light beam before it enters the relative orientation means (prisms). By correcting the astigmatism aberration in advance, before the divergent beam passes through the prisms, the subsequent amplification of aberrations by the orientation means is significantly reduced, preserving image quality across the wide field of view.
3Manufacturing precision
If optical correction means are placed after relative orientation means, then aberration correction is achieved, but manufacturing complexity increases due to specific processing of each prism
Solution Approach 1:
Instead of modifying each prism individually (which would increase device complexity), a single optical correction means is introduced as an intermediary element before the prisms. This approach achieves the same aberration correction effect while maintaining simpler manufacturing processes and device architecture.
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 solution effectively eliminates astigmatism defects generated by the window and relative orientation means, simplifying manufacturing and integration while maintaining high image quality and sighting performance, and can be easily adapted to different window shapes and orientations.
Implementation Method 1
the optical correction means are arranged between the window and the relative orientation means so that the said means of optical correction form with said window an at least substantially afocal optical system
Implementation Method 2
a lens whose power and sign are respectively substantially equal and opposite to those of the window
Data Source
Figure 1
Figure 2~3
AI summary
The method involves arranging an optical aberration defect correction unit i.e. correction lens (7), between a hemispherical dome shaped window (3) and a relative orientation unit (5) used for orienting an observation plane (4) with respect to a field, such that the correction unit forms an afocal optical system with the window, where the window and the lens are respectively divergent and convergent. Power and sign of the correction unit are equal and opposite to power and sign of the window. An independent claim is also included for an optical device for observing a field through a dome shaped window, comprising an optical correction unit.