Hybrid FMCW Pulse LiDAR Ranging for Robust Focus Adjustment
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Solution Overview
Problem
Existing laser distance measurement devices face challenges in maintaining high measurement accuracy and mobility due to varying distances and complex shapes of structures, particularly in detecting delamination in concrete structures, which requires precise focusing that is difficult with separate distance measurement devices.
Innovation Solution
A laser distance measurement device comprising a laser light source that emits first laser light of a frequency-modulated continuous wave mode; an intensity modulator that periodically modulates an intensity of the first laser light to generate pulsed second laser light; a first distance measurement instrument that generates an interference light by incidence of first measurement instrument that detects a beat frequency; and a second distance measurement instrument that measures a round-trip time of a pulse component included in the first measurement object based on the emission timing of the second laser light from the intensity of the first measurement object based on the round-trip time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate distance measurement device is provided for focus adjustment, then measurement accuracy is improved, but device size increases and mobility deteriorates
Solution Approach 1:
The patent combines the distance measurement function and focus adjustment function into a single integrated LiDAR device. The controller uses distance information from the distance measurement unit to automatically adjust the focus lens position, eliminating the need for a separate distance measurement device while maintaining measurement accuracy and improving mobility.
2Measurement precision
If precise focusing is maintained for high measurement accuracy, then measurement precision is improved, but measurable distance range is limited
Solution Approach 1:
The patent implements dynamic focus adjustment based on measured distance. The controller automatically changes the focus lens position according to the distance to the measurement object, allowing the LiDAR to maintain precise focusing and high measurement accuracy across a wide range of distances, from close to far targets.
3Adaptability or versatility
If the structure shape changes and distance varies rapidly, then adaptability is improved, but measurement accuracy deteriorates due to focus issues
Solution Approach 1:
The patent implements a feedback control mechanism where the distance measurement unit continuously measures the distance to the measurement object, and the controller uses this feedback information to automatically adjust the focus lens position. This closed-loop control ensures measurement accuracy is maintained even when the structure shape changes and distance varies rapidly.
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 accurate and robust distance measurement by combining FMCW and ToF methods, allowing precise focusing and maintaining high accuracy across varying distances, while being miniaturized for improved mobility and adaptability to diverse structural shapes.
Implementation Method 1
a laser light source that emits first laser light of a frequency-modulated continuous wave (FMCW) mode
Implementation Method 2
an intensity modulator that periodically modulates an intensity of the first laser light to generate pulsed second laser light
Implementation Method 3
a first distance measurement instrument that generates an interference light by incidence of first measurement light obtained from the second laser light and first reference light obtained from the first laser light, that detects a beat frequency included in the interference light
Implementation Method 4
detects a beat frequency included in the interference light
Implementation Method 5
a second distance measurement instrument that measures a round-trip time of a pulse component included in the first measurement light to the measurement object based on information regarding an emission timing of the second laser light from the intensity modulator and the pulse component
Data Source
AI summary
Provided are a miniaturized laser distance measurement device, a laser distance measurement method, and a program that can perform measurement robust to a change in a distance to a measurement object. A laser distance measurement device includes a laser light source that emits first laser light of an FMCW method, an intensity modulator that periodically modulates an intensity of the first laser light to generate pulsed second laser light, a first distance measurement instrument (F4) that detects a beat frequency included in interference light and that acquires first distance information to a measurement object based on the beat frequency, and a second distance measurement instrument (F5) that measures a round-trip time of a pulse component to the measurement object and that acquires second distance information to the measurement object based on the round-trip time.