Sub-pixel Centroiding Algorithm for Laser Beam Pointing Accuracy
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Solution Overview
Problem
Existing countermeasure systems face challenges in accurately directing a pencil-thin laser beam onto an incoming missile target due to limited resolution of focal plane arrays, which restricts the ability to concentrate sufficient energy on the missile's seeker, especially when the target has a large thermal signature, and requires sub-pixel level accuracy to overcome pixel-level resolution limitations.
Innovation Solution
The algorithm calculates the center of energy of the IR image, allowing for interpolation to an accuracy better than a pixel level, thereby narrowing the effective Instantaneous-Field-of-View (IFOV) and enabling precise aiming of the pencil-thin laser beam directly onto the missile seeker head, utilizing a 3x3 focal plane array portion to determine the centroid of the image with sub-pixel resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a pencil-thin laser beam is used to concentrate energy on the target, then the jamming effectiveness is improved, but the pointing accuracy requirement becomes extremely stringent (less than 0.25 pixel IFOV)
Solution Approach 1:
The patent replaces traditional mechanical/optical centroid determination methods with a computational approach. By using a processor to calculate the center of energy from pixel intensity data, the system achieves sub-pixel pointing accuracy (less than 0.25 pixel IFOV) without requiring mechanical precision adjustments. This computational substitution enables the pencil-thin laser beam to be accurately directed while maintaining manageable pointing accuracy requirements.
2Measurement precision
If a large focal plane array is used to improve resolution, then the target position can be determined more accurately, but the cost and weight increase significantly
Solution Approach 1:
The patent creates a computational model (center of energy calculation) that replicates the functionality of a high-resolution large array using data from a smaller array. By processing the intensity values from existing pixels to determine sub-pixel positioning, the system achieves the measurement precision of a large array without the associated weight and cost, effectively creating a virtual high-resolution representation from lower-resolution input data.
Solution Approach 2:
The patent changes the parameter of resolution from being determined by physical pixel size and array dimensions to being determined by computational processing capability. By calculating the center of energy using intensity-weighted positioning algorithms, the system achieves sub-pixel resolution (better than 0.25 pixel IFOV) from a small 128x128 array, transforming the resolution limitation from a physical constraint to a computational solution.
3Ease of manufacture
If a small focal plane array is used to reduce cost and weight, then the system becomes more affordable, but the resolution is limited to pixel level accuracy
Solution Approach 1:
The patent fundamentally changes the parameter of resolution from being fixed by physical pixel dimensions to being determined by computational algorithms. By implementing center of energy calculations that process intensity data across multiple pixels, the system achieves sub-pixel accuracy (less than 0.25 pixel IFOV) from a small 128x128 array, effectively decoupling resolution from array size and enabling high precision with compact, affordable hardware.
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 approach achieves accurate determination of the laser pointing direction and target position to less than 0.25 pixel IFOV, ensuring the pencil-thin laser beam is effectively directed onto the missile seeker, enhancing jamming efficiency by concentrating energy on the target while minimizing the beam's size and power requirements.
Implementation Method 1
detector arrays used in countermeasure systems employ a focal plane array onto which energy is imaged
Implementation Method 2
infrared laser radiation is projected towards the target with a so-called jam code which confuses the seeker in the missile
Data Source
AI summary
A centroiding method is provided for an optical tracking system including a laser used for countermeasuring purposes in which a pencil thin laser beam is accurately positioned onto a target through the use of centroiding techniques for ascertaining the position not only of the target but also the laser beam, with the centroiding techniques resulting in a sub-pixel level resolution. The sub-pixel resolution permits utilization of smaller cost-effective focal plane arrays by giving the small focal plane array a resolution associated with much larger focal plane arrays.