Ellipsometric Roll Sensor for Moving Platforms
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Solution Overview
Problem
Existing methods for determining the rotational orientation of a moving platform, such as missiles, are often large, costly, power-intensive, and difficult to implement in turbulent conditions, especially for small and rapidly spinning projectiles.
Innovation Solution
A compact, low-cost sensor system using an ellipsometric detector with a venetian blind component and polarizing beamsplitter to measure the polarization state of a linearly polarized laser beam, allowing for determination of the platform's rotational orientation with respect to a predefined coordinate system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radar systems are used to determine rotational orientation, then orientation data can be obtained, but the system becomes large, costly, power-intensive, and easy to detect
Solution Approach 1:
The patent replaces complex mechanical/radar systems with an optical-based ellipsometric detector that uses polarized light to measure rotational orientation. The system uses optical components (polarizing beamsplitter, quarter-wave plate, photodetectors) instead of radar hardware, achieving the same measurement function with significantly reduced size, cost, and power consumption.
Solution Approach 2:
The invention uses a simplified optical model that copies the essential measurement function of radar systems. Instead of using actual radar waves and complex signal processing, the patent creates an optical analog using polarized light reflection properties to determine orientation, achieving equivalent functionality with simpler means.
2Measurement precision
If accelerometers, gyroscopes, or magnetometers are affixed to the platform, then rotational orientation can be measured, but the devices become expensive, bulky, and complex
Solution Approach 1:
The patent replaces mechanical sensors (accelerometers, gyroscopes, magnetometers) with an optical measurement system. The ellipsometric detector uses optical reflection properties to measure orientation without mechanical moving parts or complex electronic sensors, eliminating the need for bulky and expensive inertial measurement units.
Solution Approach 2:
The system uses the target surface itself as part of the measurement mechanism. The polarized light reflects off the target surface, and the surface's optical properties (ellipsometric parameters) provide the measurement information. This eliminates the need for separate, complex sensing components that would otherwise be required.
3Measurement precision
If imaging methods are used to determine rotational orientation, then orientation data can be obtained, but it becomes difficult or impossible under turbulent conditions or for small, rapidly spinning projectiles
Solution Approach 1:
The patent uses periodic modulation of the polarized light beam to actively probe the target surface. By modulating the polarization state and measuring the reflected light's ellipsometric parameters, the system can track rapid rotational changes and turbulent conditions, providing reliable measurements where passive imaging fails.
Solution Approach 2:
The system measures changes in optical parameters (polarization state, ellipsometric angles) rather than relying on visual imaging. This allows the measurement to continue under turbulent conditions where imaging would fail, as the optical parameter changes can be detected even when the target is small, moving rapidly, or in adverse environmental conditions.
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 sensor system provides robust and accurate rotational orientation data, resolving the issues of size, cost, and operational complexity, and can function effectively even in challenging conditions.
Implementation Method 1
a venetian blind component through which the detected polarized beam passes, arranged such that the intensity of the beam after it passes through the component varies with the incident angle of the detected beam with respect to the moving platform
Implementation Method 2
a polarizing beamsplitter which receives the detected beam after it passes through the venetian blind component and splits the beam into first and second components having orthogonal circular polarizations
Implementation Method 3
an ellipsometric detector, capable of 1) detecting a polarized beam of electromagnetic radiation when the ellipsometric detector is within the line-of-sight of the polarized beam, and 2) measuring the beam's polarization state, such that the polarization state indicates the rotational orientation of the moving platform
Data Source
AI summary
A moving platform roll sensor system comprises an ellipsometric detector capable of detecting a polarized beam within the detector's line-of-sight, and measuring the beam's polarization state, such that the polarization state indicates the rotational orientation of the moving platform with respect to a predefined coordinate system. The ellipsometric detector comprises a venetian blind component through which the polarized beam passes, arranged such that the intensity of the exiting beam varies with its incident angle with respect to the moving platform, a polarizing beamsplitter which splits the exiting beam into components having orthogonal circular polarizations, the relative intensities of which vary with the relative polarization vector of the beam, and first and second detectors which receive the first and second orthogonal circular components and generate respective outputs that vary with the intensities of their received components. The beamsplitter preferably comprises a quarter wave plate and a polarization grating.