Coded Aperture Seeker for GPS-Denied Munition Navigation
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Solution Overview
Problem
There is a need for improved navigational accuracy and correction of inertial measurements in GPS-denied environments, particularly for guided munitions, while also requiring a reduction in package size and an increase in capabilities.
Innovation Solution
A guided munition system equipped with laterally facing coded aperture imaging devices and a spatial light modulator, which uses focal plane arrays sensitive to short-wave infrared wavelengths to provide image-based control for navigation, allowing for the collection and processing of celestial and terrain images to determine direction, orientation, and rotational position, even in spinning or spin-stabilized platforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional imaging devices are used for navigation in guided munitions, then navigation capability is provided, but package size cannot be reduced and navigational accuracy in GPS-denied environments is insufficient
Solution Approach 1:
The imaging device is segmented into a coded aperture mask with multiple independent aperture elements and a focal plane array sensor. This segmentation allows the system to achieve high navigational accuracy through multiple baseline measurements while maintaining a compact form factor, as each aperture element can be small and distributed across a limited area.
Solution Approach 2:
The patent transitions from traditional single-lens imaging to a coded aperture approach that utilizes the spatial dimension of light propagation. By encoding spatial information through the aperture mask pattern and recovering it through computational algorithms, the system achieves enhanced measurement precision without increasing physical size, effectively adding a computational dimension to the optical system.
2Illumination intensity
If conventional aperture designs are used, then simple structure is maintained, but field of view is limited and image distortion is high
Solution Approach 1:
The coded aperture mask employs a dynamic pattern design where the aperture distribution is optimized for different viewing angles and ranges. The mask pattern can be designed to adapt to the spinning motion of the munition, maintaining optimal field of view and minimizing distortion throughout the rotation cycle without requiring mechanical adjustment mechanisms.
Solution Approach 2:
The patent utilizes parameter changes in the aperture mask design, specifically varying the size, shape, and distribution of aperture elements across the mask surface. This parameter optimization allows the system to maximize field of view while controlling image distortion, achieving better performance than conventional fixed aperture designs without proportionally increasing structural complexity.
3Reliability
If inertial navigation alone is used, then system simplicity is maintained, but navigational drift occurs over time
Solution Approach 1:
The coded aperture imaging device provides continuous visual feedback for navigation by capturing images of the terrain and celestial bodies. This feedback is processed to determine the munition's position, orientation, and velocity, correcting inertial navigation drift in real-time. The system establishes a feedback loop where imaging data continuously refines the navigation solution, maintaining high reliability over extended periods.
Solution Approach 2:
The imaging device serves multiple functions simultaneously: it provides navigation information for position and orientation determination, enables terrain matching for course correction, and offers celestial body recognition for GPS-denied navigation. This multi-functionality allows the system to achieve high navigational reliability without proportionally increasing complexity, as a single device performs multiple navigation tasks.
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 solution enhances navigational accuracy and adaptability by maximizing the field of view, reducing image distortion, and enabling navigation in GPS-denied environments, while allowing for a compact design that can integrate multiple sensors for comprehensive data collection and situational adaptability.
Implementation Method 1
The coded aperture can include a spatial light modulator (SLM) configured to change the pattern in the mask
Implementation Method 2
The sensor can include a focal plane array (FPA). The FPA can be sensitive to short-wave infrared (SWIR) wavelengths
Data Source
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AI summary
A guided munition system includes a munition body including at least one fluid dynamic control for changing course of the munition body in flight. A seeker onboard the munition body is operatively connected to control the at least one fluid dynamic control. The seeker includes a coded aperture imaging device facing outward from the munition body for image based control for guiding the munition body in flight.