Frequency Selective MMW Source for Concealed Object Detection
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Solution Overview
Problem
Current systems for detecting concealed objects using millimeter and sub-millimeter waves face challenges in accurately identifying and locating objects without generating false positives, particularly in varying clothing and object compositions.
Innovation Solution
A portal system utilizing an electrooptic source with an optical signal generator, optical switching and encoding circuitry, and optical/electrical converters to generate modulated millimeter or sub-millimeter waves, which are directed through detectors to analyze reflections and determine the presence of concealed objects by comparing frequency-dependent attenuation and reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single frequency millimeter wave source is used for detection, then the device complexity is reduced, but the measurement precision and ability to differentiate between objects and clothing is insufficient leading to false positives
Solution Approach 1:
The millimeter wave source is segmented into multiple discrete frequency components using an optical frequency comb generator. Each comb line represents a distinct frequency that can be independently selected and combined, allowing the system to transmit multiple frequencies through a single waveguide while maintaining detection accuracy and reducing false positives.
Solution Approach 2:
Multiple frequency components are merged into a single millimeter wave signal by combining optical comb lines and converting them to microwave frequencies. This merging process allows the system to maintain the benefits of multiple frequencies for accurate differentiation while using a single integrated waveguide and detector system, thus managing device complexity.
2Measurement precision
If multiple frequencies are used to differentiate objects from clothing, then the measurement precision improves, but the loss of time increases due to sequential frequency scanning
Solution Approach 1:
The system uses periodic modulation of the optical comb lines to generate time-varying millimeter wave signals at multiple frequencies. By modulating different comb lines with different frequencies and phases, the system can transmit multiple frequency components simultaneously or in rapid succession, reducing the time penalty associated with frequency scanning while maintaining accurate object differentiation.
Solution Approach 2:
The optical frequency comb is generated and configured in advance before detection begins. The comb lines are pre-established with known frequency spacing and can be rapidly switched or combined without requiring time-consuming frequency synthesis during the actual detection process, thus minimizing detection time while maintaining precision.
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 system effectively reduces false positives by using multiple frequencies to differentiate between clothing, objects, and concealed items, providing accurate detection of concealed objects without human interpretation, and can be configured for self-calibration and imaging capabilities.
Implementation Method 1
the optical circuitry is configured to permit the selection and combination of different ones of the distinct-frequency optical outputs to generate a modulated optical signal, which is converted to a millimeter or sub-millimeter wave
Implementation Method 2
directed through detectors to analyze reflections and determine the presence of concealed objects by comparing frequency-dependent attenuation and reflectivity
Data Source
AI summary
The present invention relates to the design and operation of a frequency selective electrooptic source. In accordance with one embodiment of the present invention, the electrooptic source comprises an optical signal generator, optical circuitry, and at least one optical/electrical converter wherein the optical signal generator comprises a plurality of optical outputs characterized by distinct output frequencies and the optical circuitry is configured to permit the selection and combination of different ones of the distinct-frequency optical outputs to generate a modulated optical signal, which is converted to a millimeter or sub-millimeter wave. Additional embodiments are disclosed and claimed.