Dual-Comb Laser Ranging for Kilometer-Scale Ambiguity-Free Measurement
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Solution Overview
Problem
Existing laser-based distance measuring technologies using dual optical frequency combs face limitations such as ambiguity range that is too low for many applications, require complex and expensive spectral filtering, are not robust against drifts, and are not suitable for measuring moving targets or long distances without additional calibration.
Innovation Solution
A method and device that uses separate radiation splitters to split dual comb radiation into distinct signal and local oscillator portions, ensuring correct superimposition without relying on polarization, allowing simultaneous measurement of distances up to 1 km without ambiguity and without the need for calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral filtering is used to split frequency combs, then the measurement can be carried out, but the system becomes complex and expensive and resolution is reduced by limiting bandwidth
Solution Approach 1:
The patent replaces the optical spectral filtering system with a purely electronic signal processing system. The two frequency combs are combined without spectral filtering, and the separation of signal components is achieved through electronic correlation processing of the detected interference signals, eliminating complex optical filters while maintaining measurement precision
Solution Approach 2:
The patent changes the approach from optical domain filtering to temporal/electronic domain processing. By detecting the full spectral content and processing it electronically with correlation methods, the system achieves the same separation function without the bandwidth limitations and complexity of optical filters
2Measurement precision
If two measurements are carried out in close succession using the Vernier effect, then the ambiguity range is extended, but the measurement becomes slow and requires additional switching mechanism
Solution Approach 1:
The patent merges the two measurement channels into a single simultaneous measurement process. Both frequency combs are combined and measured together in one interferometric detection, eliminating the need for sequential switching and enabling high-speed measurement of moving targets while maintaining absolute distance measurement capability
Solution Approach 2:
The patent enables continuous measurement by eliminating the switching mechanism. Both frequency comb signals are present and measured simultaneously in a continuous process, allowing real-time tracking of moving targets without interruption or time delay
3Ease of operation
If polarization is used to distinguish between local oscillators, then the system can operate, but it is not robust against polarization drifts and unwanted polarization rotations
Solution Approach 1:
The patent replaces the polarization-based discrimination mechanism with an electronic correlation-based discrimination mechanism. The system no longer relies on polarization states to distinguish between the two local oscillators, but instead uses temporal correlation of the interference signals with the known frequency comb structures, making the system immune to polarization effects
Solution Approach 2:
The patent introduces electronic correlation processing as an intermediary between the optical interference detection and the final measurement result. This electronic processing step acts as a robust discriminator that is insensitive to polarization variations, replacing the fragile polarization-based discrimination
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
Enables accurate and robust distance measurement of up to 1 km with simultaneous detection of moving targets, overcoming limitations of previous methods by ensuring correct superimposition and reducing complexity and cost.
Implementation Method 1
a dual comb radiation source (1) emitting two radiation portions (11, 12), each being a train of laser pulses, with the pulse repetition frequencies being slightly offset between the two trains
Implementation Method 2
devices based on dual optical frequency comb technology
Implementation Method 3
a first radiation splitter (6, 7) connected to a first output port of the dual comb radiation source (1) and splitting a first one of the two radiation portions (11) into a first signal radiation portion (21) and a first local oscillator radiation portion (23)
Implementation Method 4
The combined signal radiation is directed onto an object, the distance to which is to be measured
Implementation Method 5
Receiving a signal thrown back from the object irradiated by the combined signal radiation. Splitting the signal into a first signal portion and a second signal portion. Superimposing, by the first radiation splitter, the first signal portion with the second local oscillator radiation portion to generate a first measurement signal
Data Source
AI summary
A laser distance ranging method includes splitting two combs of dual comb radiation into a signal radiation portion and a local oscillator radiation portion. The signal radiation portions are, after separation, combined into a combined signal radiation and directed onto an object, the distance to which is to be measured. The signal thrown back from the object is split into a first and second signal portions. The first signal portion is superimposed with the second local oscillator radiation portion to generate a first measurement signal, and the second signal portion is superimposed with the first local oscillator radiation portion to generate a second measurement signal. The distance to the object is determined from the first and second measurement signals, and from reference signals obtained by the partial reflection, wherein the Vernier effect can be used to extend ambiguity by comparison of the first and second measurement signals.