FDDM-CC Signal Generation for Sub-Micrometer Distance Measurement
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Solution Overview
Problem
Current distance measurement technologies for high precision, such as optical continuous wave laser links and femtosecond pulse lasers, are complex, costly, and limited in resolution and applicability for absolute distance measurements and clock synchronization, especially in space-related applications.
Innovation Solution
The Frequency Domain Distance Measurement Cross Correlation (FDDM-CC) method uses a simple optical setup to generate a signal by combining laser pulses and calculating differences between harmonics of a voltage signal, enabling high-resolution absolute distance measurements and clock synchronization with low light intensities, and can be applied for fiber stabilization and frequency transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical continuous wave laser links are used for distance measurement, then measurement precision is improved (50 nm to pm resolution), but device complexity increases and the system becomes highly dependent on laser noise
Solution Approach 1:
The patent uses periodic pulse trains instead of continuous wave lasers. By transmitting periodic pulses and analyzing the cross-correlation of reflected pulses, the system achieves high precision distance measurement while reducing dependence on laser noise characteristics and simplifying the overall system design.
Solution Approach 2:
The patent replaces complex optical continuous wave systems with a simpler pulsed laser system combined with electronic cross-correlation processing. This substitution of the measurement approach reduces device complexity while maintaining or improving measurement precision through time-domain analysis rather than continuous optical interference.
2Measurement precision
If femtosecond pulse lasers are used for absolute distance measurement, then measurement precision is improved (sub-micrometer resolution), but device complexity and cost increase
Solution Approach 1:
The patent uses standard pulsed lasers with longer pulse durations (nanosecond to microsecond range) instead of expensive femtosecond lasers. The cross-correlation technique compensates for the reduced temporal resolution, achieving high precision distance measurement with simpler, more cost-effective laser sources.
Solution Approach 2:
The patent introduces an intermediary processing step - electronic cross-correlation of the received pulse train - that enables high precision measurement without requiring ultra-short pulses. This intermediary signal processing technique acts as a mediator between the simple pulsed laser transmission and the precise distance measurement requirement.
3Device complexity
If RF-links are used for distance measurement, then device complexity is reduced, but measurement precision deteriorates (100 μm resolution)
Solution Approach 1:
The patent employs periodic pulsed laser transmission and analyzes the temporal structure of reflected pulses through cross-correlation. This periodic approach enables precision in the micrometer to sub-micrometer range, significantly improving upon RF-link performance while maintaining relatively simple system architecture.
Solution Approach 2:
The patent replaces RF-link based measurement systems with optical pulsed laser systems combined with electronic cross-correlation processing. This substitution improves measurement precision by orders of magnitude while keeping the overall system complexity manageable through time-domain signal processing.
4Measurement precision
If three frequency comb lasers are used for clock synchronization, then synchronization precision is improved (femtosecond level), but device complexity increases
Solution Approach 1:
The patent merges distance measurement and clock synchronization functions into a single cross-correlation-based system. By analyzing the temporal correlation of pulse trains, the system simultaneously achieves both functions with reduced complexity compared to separate frequency comb laser systems.
Solution Approach 2:
The patent creates a universal measurement system that performs both absolute distance measurement and clock synchronization using the same hardware platform and cross-correlation processing technique. This multi-functional approach eliminates the need for separate frequency comb lasers while maintaining high precision for both applications.
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
FDDM-CC provides sub-micrometer distance resolution, is cost-efficient, and robust, improving clock synchronization and distance measurement accuracy while being applicable for various space-related projects, including satellite and terrestrial applications.
Implementation Method 1
A detector is adapted to combine the first laser pulses and the second laser pulses and transform the combined laser pulses into a voltage signal
Data Source
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Figure 3
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AI summary
An apparatus for generating a Frequency Domain Distance Measurement Cross Correlation, FDDM-CC, signal. The apparatus comprises a first input terminal adapted to receive first laser pulses and a second input terminal adapted to receive second laser pulses. A detector is adapted to combine the first laser pulses and the second laser pulses and transform the combined laser pulses into an electrical signal. A controller is adapted to transform the electrical signal to the frequency domain and calculate a difference between two different harmonics of the electrical signal in frequency domain as the FDDM-CC signal.