Dual-Modulation Distance Measurement for Range and Resolution
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Solution Overview
Problem
Existing distance measurement devices using light face a trade-off between measurable distance range and resolution, with existing FMCW schemes limiting both parameters.
Innovation Solution
A distance measurement device employing multiple phase modulation through long-period internal and short-period external modulation of light signals, allowing simultaneous calculation of long and short period data to secure both range and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FMCW scheme uses single frequency modulation, then device complexity is reduced, but measurement precision deteriorates due to trade-off between measurable distance and resolution
Solution Approach 1:
The patent divides the single modulation function into two separate modulation stages: first modulation unit performs initial frequency modulation, and second modulation unit performs additional frequency modulation. This segmentation allows each unit to operate at optimized frequencies, achieving high measurement precision without requiring a single complex modulation system.
Solution Approach 2:
The patent employs periodic frequency modulation with specific sweep frequencies in each modulation unit. The first modulation unit operates at a lower sweep frequency for long-range measurement, while the second modulation unit operates at a higher sweep frequency for high-resolution measurement. This periodic action at multiple frequency levels resolves the trade-off between measurement range and precision.
2Length of stationary object
If FMCW scheme increases frequency sweep range, then measurable distance increases, but resolution deteriorates
Solution Approach 1:
The patent segments the frequency sweep function into two independent modulation units. The first modulation unit provides a wide frequency sweep for extended measurement range, while the second modulation unit provides a narrower, higher-frequency sweep for enhanced resolution. This segmentation eliminates the traditional trade-off by operating at multiple frequency levels simultaneously.
Solution Approach 2:
The patent transitions from single-dimensional frequency modulation to two-dimensional frequency modulation by adding a second modulation stage. This dimensional expansion allows independent optimization of measurement range (first modulation) and resolution (second modulation) without the constraints of single-frequency sweeping.
3Measurement precision
If FMCW scheme uses multiple modulation stages, then both range and resolution are improved, but device complexity increases
Solution Approach 1:
The patent combines two separate modulation units into a unified laser radar system where the output of the first modulation unit feeds directly into the second modulation unit. This merging approach achieves enhanced measurement capability while avoiding the complexity of completely separate systems, as the modules are integrated into a single optical path.
Solution Approach 2:
The patent designs the modulation units to be multi-functional: the first modulation unit serves both as a frequency shifter and as a range-extending mechanism, while the second modulation unit simultaneously provides resolution enhancement and acts as a frequency modulator. This universality reduces overall system complexity by making each component perform multiple functions.
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 both long-distance measurement capability and high resolution by aligning phases of reference and reflected light, simplifying calculations and maintaining waveform integrity.
Implementation Method 1
a light source unit configured to generate light whose wavelength is modulated with time through internal modulation based on the first signal
Implementation Method 2
a modulation unit configured to further modulate, with time, the wavelength of the light output from the light source unit using a Doppler effect through external modulation based on the second signal
Implementation Method 3
a detection unit configured to detect interference light between reflected light obtained by the measurement light being reflected by the target object and the reference light
Data Source
AI summary
A device includes a signal generation unit that generates a first signal having a first repetition frequency and a second signal having a second repetition frequency higher than the first repetition frequency, a light source unit that generates light whose wavelength is modulated with time through internal modulation based on the first signal, a modulation unit that further modulates, with time, the wavelength of the light using a Doppler effect through external modulation based on the second signal, a splitting unit that divides the light output from the modulation unit into measurement light and reference light, an irradiation unit that irradiates a target object with the measurement light, a detection unit that detects interference light between reflected light from the target object and the reference light, and a calculation unit that calculates a distance to the target object on the basis of an output signal from the detection unit.