Optical Comb Frequency Switching for Phase-Offset Distance Measurement
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Solution Overview
Problem
Conventional optical comb distance meters face challenges in achieving high accuracy for long-distance measurements and are prone to phase offsets due to signal transmission paths other than the target object, especially when measuring moving objects.
Innovation Solution
An optical comb generation device with multiple optical comb generators driven by modulation signals phase-locked to a reference frequency, using a drive control unit to cyclically switch modulation frequencies, reducing phase offsets and enabling accurate distance measurements even with moving objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical comb generators are used for absolute distance measurement, then measurement capability is provided, but phase offsets from signal transmission paths cause measurement errors
Solution Approach 1:
The patent segments the distance measurement into multiple discrete steps by cyclically switching between different optical comb generators with distinct modulation frequencies. Each generator measures a portion of the total distance, and the results are synthesized to obtain the complete absolute distance while eliminating phase offset errors through the segmentation approach.
Solution Approach 2:
The patent changes the modulation frequency parameter of the optical comb generators cyclically. By switching between generators with different modulation frequencies (e.g., 10 MHz, 20 MHz, 30 MHz), the system resolves phase ambiguities and eliminates phase offset errors from signal transmission paths, thereby improving measurement reliability while maintaining precision.
2Length of stationary object
If modulation frequency switching is performed for absolute distance measurement, then measurement range is extended, but measuring time increases
Solution Approach 1:
The patent employs periodic action by cyclically switching between multiple optical comb generators with different modulation frequencies in a predetermined sequence. This periodic switching enables the system to extend the measurable distance range through multiple frequency steps while reducing total measurement time compared to sequential single-frequency methods, as the switching is optimized and repeated efficiently.
3Device complexity
If single optical comb generator is used, then device complexity is reduced, but measurement accuracy for moving objects deteriorates
Solution Approach 1:
The patent introduces dynamics by implementing rapid cyclic switching between multiple optical comb generators with different modulation frequencies. This dynamic switching capability allows the system to adapt to moving objects by completing measurements within short time intervals, thereby maintaining measurement precision for moving targets while managing device complexity through coordinated control of the multiple generators.
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 device achieves high-accuracy absolute distance measurements with reduced phase offsets and shortened measuring times, expanding the measurable range to 300 meters and accommodating moving targets.
Implementation Method 1
respectively modulating a phase or an intensity periodically
Implementation Method 2
respectively modulating a phase or an intensity periodically
Implementation Method 3
emitting pulses of a reference light and a measuring light with a coherence
Implementation Method 4
a reference light detector detects an interference light of a reference light pulse and a measuring light pulse
Data Source
AI summary
A purpose of the present invention is to provide an optical comb generation device capable of obtaining an absolute distance result with high accuracy by reducing a phase offset by a signal transmission path of an object other than an object to be measured, for example in an optical comb distance meter for measuring a distance from a time difference between an interference signal of a measuring light and an interference signal of a reference light. A drive control unit controls to output M (M is an integer of two or more) types of optical combs with mutually different modulation frequencies in which N (N is an integer of three or more) types of modulation frequencies are switched cyclically, by respectively modulating a phase or an intensity periodically, from M optical comb generators, by supplying driving signals to the M optical comb generators comprised in an optical comb generation unit.