Offset Aperture Blocking Component for Refractive Optics Specular Return
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Solution Overview
Problem
Two-dimensional wide field-of-view refractive imagers face the challenge of specular return or retro-reflection from the imaging sensor, which can easily reveal the imager's location, and existing solutions like multiple wedges are ineffective and detrimental to image quality, especially in large field-of-view applications.
Innovation Solution
An optical design where the operational aperture is offset from the primary optical axis and has a blocking component, such as an absorptive coating, to absorb specular reflections, reducing the optical cross-section and making the imager harder to detect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If multiple wedges are used to eliminate specular return, then retro-reflection is reduced, but image quality and distortion worsen
Solution Approach 1:
The patent extracts the harmful specular return path from the optical system by introducing a blocking component that selectively intercepts reflected light while leaving the imaging path uninterrupted. This separates the function of light blocking from the function of image formation, eliminating the need for wedges that compromise image quality.
Solution Approach 2:
The blocking component is positioned asymmetrically relative to the optical axis, specifically in the upper half of the entrance aperture while the operational aperture is in the lower half. This asymmetric placement targets the specular return paths that reflect back through the upper aperture region, effectively blocking them without interfering with the symmetric imaging path.
2Object-generated harmful factors
If multiple wedges are used to eliminate specular return, then retro-reflection is reduced, but device complexity increases
Solution Approach 1:
The blocking component is merged with the entrance aperture structure, combining the functions of light blocking and aperture definition into a single integrated element. This eliminates the need for separate wedge components and simplifies the overall optical assembly while maintaining effective specular return blocking.
3Object-generated harmful factors
If multiple wedges are used to eliminate specular return, then retro-reflection is reduced, but reliability decreases in cold Dewar
Solution Approach 1:
The patent removes the wedge component entirely from the system and replaces it with a blocking component that is part of the fixed entrance aperture structure. This extraction of the problematic wedge element eliminates the reliability issues associated with wedge movement in cold Dewar environments while maintaining the specular return blocking function.
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 design significantly reduces or eliminates specular return, making it much more difficult to detect the imager, while maintaining image quality and optical performance.
Implementation Method 1
the blocking component being configured to absorb surface reflections from the imaging detector
Implementation Method 2
refractive optics having an entrance aperture and configured to receive optical radiation via an operational aperture, to focus the optical radiation onto a focal plane
Data Source
AI summary
An optical imaging system including refractive optics and a blocking component. The refractive optical having an entrance aperture and configured to receive optical radiation via an operational aperture, to focus the optical radiation onto a focal plane to form a telecentric image plane co-located with the focal plane, the operational aperture being co-located with the entrance aperture, having a diameter less than half a diameter of the entrance aperture, and being offset from a primary optical axis that bisects the entrance aperture by at least a radius of the entrance aperture, and a blocking component located at the entrance aperture on an opposite side of the primary optical axis from the operational aperture. The blocking component being configured to block the optical radiation from exiting the refractive optics via a region of the entrance aperture where the blocking component is located.