Free Space Optical Beacon Tracking via Video Image Registration
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Solution Overview
Problem
Conventional free-space optical (FSO) systems face challenges in optical alignment due to high directionality and precision requirements, which can lead to degraded signal acquisition and tracking, especially with misalignment and noise from common cathodes in position sensing detectors.
Innovation Solution
A video tracking system and method using a camera and controller in each FSO terminal to capture and process frames, analyze interim images, and output coordinates to a mirror package for precise beam steering, enhancing signal-to-noise ratio and rejecting clutter through image registration, frame subtraction, thresholding, accumulation, and morphological operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional position sensing detectors with common cathode are used, then the system can detect optical signals, but the noise floor is limited to higher levels which degrades the acquisition and tracking link margin
Solution Approach 1:
The patent segments the detection function by separating the beacon detection path from the data communication path. The beacon detector uses a photodiode that is spatially and functionally separated from the data link detectors, eliminating the common cathode noise issue while maintaining detection capability.
Solution Approach 2:
The patent extracts the beacon detection function from the data link detection system. By using a dedicated beacon detector with its own photodiode and signal processing path, the system removes the harmful common cathode noise from the beacon detection process while preserving the data link functionality.
2Measurement precision
If high directionality is used in the data link, then signal precision is improved, but very high precision beam steering is required which increases system complexity
Solution Approach 1:
The patent applies preliminary action by using the beacon to pre-establish the optical axis alignment before data transmission begins. The slow-axis and fast-axis alignments are performed using the beacon signal to set initial pointing angles, which simplifies the subsequent high-precision beam steering requirements for data transmission.
Solution Approach 2:
The patent introduces the beacon as an intermediary element that mediates the alignment process. The beacon serves as a reference signal that enables coarse alignment through image processing algorithms, reducing the precision burden on the beam steering elements during actual data communication.
3Reliability
If optical alignment drift occurs between optical fibers and position sensing detectors, then acquisition and tracking performance is highly degraded, but maintaining precise alignment increases system complexity and cost
Solution Approach 1:
The patent implements feedback through the beacon detection system that continuously monitors the optical alignment status. The image processing algorithms analyze the beacon position in real-time and provide feedback signals to adjust the beam steering elements, automatically compensating for drift without requiring complex manual alignment procedures.
Solution Approach 2:
The system performs self-alignment using the beacon signal and image processing algorithms. The automated tracking system continuously adjusts the beam pointing based on beacon position feedback, enabling the system to self-correct alignment drift without external intervention or complex mechanical alignment mechanisms.
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 achieves precise alignment with a signal-to-noise ratio improvement of approximately 10 to 100 micro radians, effectively rejecting unwanted signals and maintaining data link integrity by isolating and tracking beacons with optimized parameters.
Implementation Method 1
a camera of a first terminal performs two or more captures of two or more frames across/along a line of sight toward a second terminal
Implementation Method 2
The beacon may be subject to atmospheric scintillation which may cause the beacon to appear to change in intensity and/or position from frame to frame
Data Source
AI summary
A method supported by a first terminal is provided herein. To implement the method, a camera of a first terminal performs two or more captures of two or more frames along a line of sight toward a second terminal. A controller of the first terminal manipulates the two or more frames to produce two or more interim images and analyzes the two or more interim images to track a beacon of the second terminal. The controller outputs coordinates with respect to the tracked beacon to a mirror package of the first terminal.