Wide-Field Optical System Using Inverted Mirror Configuration
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Solution Overview
Problem
Wide-field-of-view optical systems, particularly those of the inverse-telephoto family, suffer from noticeable negative distortion, leading to image compression at the field of view edges, which results in decreased spatial resolution due to shorter focal lengths and increased ground sample distance, detrimental for airborne and space-borne sensing applications.
Innovation Solution
An all-reflective wide-field-of-view telescope design featuring a negative primary mirror, low optical-power secondary mirror, negative tertiary mirror, and positive quaternary mirror, configured to maintain an effective focal length at the edges of the field of view equal to that at the center, incorporating an aperture stop between the quaternary mirror and the image plane, and optionally including a spectrometer and housing for integrating the mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an inverse-telephoto optical system is used to achieve wide field of view, then the field of view is increased, but negative distortion occurs causing shorter focal length at edges and decreased spatial resolution
Solution Approach 1:
The patent inverts the conventional inverse-telephoto configuration by using a telephoto optical form instead. This means placing positive optical power elements at the front and negative optical power elements at the rear, which is the opposite of the conventional approach. This inversion allows the system to achieve wide field of view while maintaining longer focal length at the edges, thereby preserving spatial resolution.
Solution Approach 2:
The patent changes the optical parameters by using multiple mirrors with different optical powers (negative primary, low-power secondary, negative tertiary, positive quaternary) to control the effective focal length distribution across the field of view. This parameter adjustment ensures that the focal length at the edges is maintained to be at least equal to that at the center, counteracting the negative distortion inherent in conventional wide-field systems.
2Adaptability or versatility
If negative distortion is present in the optical system, then wide field of view is achieved, but ground sample distance increases at edges reducing imaging quality
Solution Approach 1:
The patent inverts the conventional approach by using positive distortion characteristics through telephoto optical form. This inversion causes the focal length to increase toward the edges of the field of view, which compensates for the increased range at edges and maintains constant ground sample distance across the entire field of view.
Solution Approach 2:
The patent applies preliminary anti-action by designing the optical system to produce positive distortion that pre-compensates for the negative distortion effects. The multiple mirrors are configured in advance to create focal length extension at the edges, which counteracts the expected increase in ground sample distance before imaging occurs.
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 ensures constant spatial resolution across the field of view by introducing positive distortion, counteracting increased range at the edges, maintaining ground sample distance, and enhancing imaging capabilities for airborne and space-borne sensing systems.
Implementation Method 1
a negative optical-power primary mirror configured to receive and reflect light from an image scene
Implementation Method 2
a low optical-power secondary mirror configured to receive and reflect light from the primary mirror
Implementation Method 3
a negative optical-power tertiary mirror configured to receive and reflect light from the secondary mirror
Implementation Method 4
a positive optical-power quaternary mirror configured to receive and reflect light from the tertiary mirror
Data Source
Figure 1a
Figure 1b~1d
Figure 2a~2b
AI summary
A wide-field-of-view (WFOV) optical system includes a negative optical-power primary mirror configured to receive and reflect light from an image scene; a low optical-power secondary mirror configured to receive and reflect light from the primary mirror; a negative optical-power tertiary mirror configured to receive and reflect light from the secondary mirror; and a positive optical-power quaternary mirror configured to receive and reflect light from the tertiary mirror. The primary, secondary, tertiary and quaternary mirrors are configured to maintain an effective focal length (EFL) at edges of the field of view (FOV) of the optical system to be at least equal to a center of the FOV of the optical system so that a spatial resolution of the optical system essentially remains constant across the FOV.