Optical Tracking System Using Non-Spot Beam Shapes
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Solution Overview
Problem
Free space optical communication systems face challenges in maintaining signal-to-noise ratio (SNR) due to mechanical motions and vibrations, which affect the precise pointing required for optical beam alignment, especially in dynamic environments like satellites in orbit.
Innovation Solution
The use of non-spot beam shapes on optical detector arrays, such as rectangular or cross-shaped beams, enhances the slope factor, leading to improved noise equivalent angle (NEA) and responsiveness, facilitating active tracking and maintaining alignment over longer distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spot beam shapes are used on optical detector arrays, then the system structure remains simple, but the noise equivalent angle is large and tracking responsiveness is poor
Solution Approach 1:
The patent changes the geometric parameter of the beam shape from circular (spot) to non-circular (rectangular, cross-shaped, or annular) to improve the slope factor. This parameter change in beam geometry directly reduces the noise equivalent angle and enhances tracking responsiveness without requiring complex additional hardware
Solution Approach 2:
The patent specifically employs annular (ring-shaped) beam profiles as a curved geometric form to optimize the slope factor. The annular shape creates favorable transfer function characteristics that reduce the noise equivalent angle while maintaining system simplicity
2Reliability
If precise pointing is required for optical beam alignment, then communication reliability improves, but mechanical vibrations and motions cause misalignment
Solution Approach 1:
The patent implements active tracking systems that use the improved detector array responses to provide feedback for real-time beam alignment correction. The enhanced slope factor from non-spot beam shapes enables more accurate detection of beam position deviations, allowing the feedback control system to compensate for mechanical vibrations and maintain reliable communication
Solution Approach 2:
By changing the beam shape parameter to non-spot configurations, the system increases the slope factor which amplifies the detector's sensitivity to angular deviations. This parameter change makes the system more responsive to tracking errors, enabling better compensation for mechanical disturbances through active control
3Speed
If tracking responsiveness is improved, then alignment maintenance over long distances is enhanced, but the system requires higher sensitivity to beam position changes
Solution Approach 1:
The patent changes the beam shape parameter to non-spot configurations (rectangular, cross-shaped, or annular) which fundamentally alters the transfer function characteristics. This parameter change increases the slope factor, simultaneously improving tracking responsiveness and the sensitivity of beam position detection
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 significantly reduces the noise equivalent angle, enhancing the system's ability to track and maintain alignment, thereby improving the reliability and efficiency of free space optical communication systems.
Implementation Method 1
an optical detector array to provide an indication of a relative alignment of the incoming light with respect to the optical detector array
Implementation Method 2
The optical elements reshape the incoming light to provide a non-spot beam shape on the optical detector array
Data Source
AI summary
An optical detector system provides output to an optical tracking system to facilitate optical communications by tracking a beam of incoming light using a fast-steering mirror (FSM). The optical detector system comprises an array of optical photodetectors, such array comprising one or more quad cells. The incoming light passes through one or more optical elements to generate a specified beam shape, such as a bar or cross, on the array. The resulting output from the array is highly responsive to changes in position of the reshaped beam on the array. As a result, noise equivalent angle (NEA) of the optical detector system representing pointing error is substantially reduced. A reduction in NEA facilitates more precise alignment, allowing incoming light to be aligned to a smaller area. For example, the incoming light may be aligned to a single mode optical fiber connected to a receiver system.