Frequency-Converted Optical Comb Generation for Stable Distance Measurement
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Solution Overview
Problem
Conventional optical comb distance meters face challenges in achieving high accuracy and stability due to relative phase noise and phase fluctuations in the driving signals of optical comb generators, leading to variations in measurement results, especially when measuring long distances quickly.
Innovation Solution
A low relative phase noise optical comb generation device is designed with at least three oscillators generating frequency signals with different frequencies, using frequency converters to reduce relative phase noise by supplying modulation signals as sum or difference frequency signals to optical comb generators, and employing band pass filters and isolators to minimize spurious components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple optical comb generators are driven by oscillators with different frequencies to enable simultaneous measurement of multiple objects, then measurement productivity is improved, but relative phase noise between driving signals increases causing measurement precision to deteriorate
Solution Approach 1:
The driving signal generation is segmented into multiple independent oscillators (first oscillator for reference signal, second oscillator for measuring signal) that can operate simultaneously at different frequencies. This segmentation allows parallel measurement of multiple objects while maintaining independent phase control for each channel, resolving the contradiction between productivity improvement through multi-frequency operation and precision maintenance through separate phase management
Solution Approach 2:
Frequency converters are introduced as intermediary devices between the oscillators and optical comb generators. These converters transform the oscillator signals into sum or difference frequency signals that drive the optical comb generators, enabling frequency conversion while maintaining phase coherence relationships. The intermediary frequency converters allow the system to operate at optimized frequencies for each measurement channel while preserving the ability to calculate accurate distance measurements
2Loss of time
If measurement time is reduced to accelerate the measurement process, then productivity is improved, but measurement precision deteriorates due to phase fluctuations in the driving signals
Solution Approach 1:
The system performs preliminary frequency conversion and phase relationship establishment before the actual distance measurement. By pre-configuring the frequency converters to generate sum or difference frequency signals with known phase relationships, the system prepares the measurement signals in advance, allowing rapid measurement execution without sacrificing precision due to phase fluctuations during the measurement process
Solution Approach 2:
The system uses feedback through frequency converters that maintain phase coherence between reference and measuring signals. The converters provide continuous phase relationship information that enables real-time correction of phase fluctuations, allowing the system to maintain high measurement precision even when measurement time is reduced. The feedback mechanism ensures that phase noise does not accumulate during rapid measurements
Data Source
AI summary
A purpose of the present invention is to provide a low relative phase noise optical comb generation device in which a repetitive frequency of an interference signal of an optical comb is stabilized by reducing a relative phase noise of driving signals with different frequencies for driving multiple optical comb generators in an optical comb distance meter. A low relative phase noise optical comb generation device, comprising: at least three oscillators 13, 13A, 13B for generating frequency signals with mutually different frequencies phase locked to a reference frequency signal F REF given by a reference oscillator 11; and at least two frequency converters 14A, 14B to which a frequency signal obtained by one oscillator 13 of the at least three oscillators and respective frequency signals obtained by respective oscillators 13A, 13B other than the one oscillator are input; wherein the at least two frequency converters 14A, 14B supply the at least two types of modulation signals, in which a relative phase noise is reduced respectively as a sum frequency signal or a difference frequency signal of the frequency signal by the one oscillator and a frequency signal by other oscillator with a lower phase noise, to at least two optical comb generators 15A, 15B as driving signals.