A novel hybrid TOF/phase-shift method for absolute distance measurement using a falling-edge RF-modulated pulsed laser

Yang, Hongzhi; Zhao, Changming; Zhang, Haiyang; Zhang, Zilong; Gui, Kun

doi:10.1016/j.optlastec.2019.01.029

Cited by 7 publications

(3 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As an active remote sensing technology, LiDAR emits laser pulses and receives their returns reflected by object surfaces [8]. The distance between the sensor and the target is generally measured by the time of flight (TOF) method or phase-shift method [9]. With the spatial position of the LiDAR as a reference, the three-dimensional (3D) coordinates of a reflection point on the target object can be accurately derived.…”

Section: Introductionmentioning

confidence: 99%

Effects of Illumination Conditions on Individual Tree Height Extraction Using UAV LiDAR: Pilot Study of a Planted Coniferous Stand

Li,

Lin,

et al. 2024

Forests

View full text Add to dashboard Cite

Tree height is one of the key dendrometric parameters for indirectly estimating the timber volume or aboveground biomass of a forest. Field measurement is time-consuming and labor-intensive, while unmanned aerial vehicle (UAV)-borne LiDAR is a more efficient tool for acquiring tree heights of large-area forests. Although individual tree heights extracted from point cloud data are of high accuracy, they are still affected by some weather and environment factors. In this study, taking a planted M. glyptostroboides (Metasequoia glyptostroboides Hu & W.C. Cheng) stand as the study object, we preliminarily assessed the effects of various illumination conditions (solar altitude angle and cloud cover) on tree height extraction using UAV LiDAR. The eight point clouds of the target stand were scanned at four time points (sunrise, noon, sunset, and night) in two consecutive days (sunny and overcast), respectively. The point clouds were first classified into ground points and aboveground vegetation points, which accordingly produced digital elevation model (DEM) and digital surface model (DSM). Then, the canopy height model (CHM) was obtained by subtracting DEM from DSM. Subsequently, individual trees were segmented based on the seed points identified by local maxima filtering. Finally, the individual tree heights of sample trees were separately extracted and assessed against the in situ measured values. As results, the R2 and RMSEs of tree heights obtained in the overcast daytime were commonly better than those in the sunny daytime; the R2 and RMSEs at night were superior among all time points, while those at noon were poorest. These indicated that the accuracy of individual tree height extraction had an inverse correlation with the intensity of illumination. To obtain more accurate tree heights for forestry applications, it is best to acquire point cloud data using UAV LiDAR at night, or at least not at noon when the illumination is generally strongest.

show abstract

Section: Introductionmentioning

confidence: 99%

Effects of Illumination Conditions on Individual Tree Height Extraction Using UAV LiDAR: Pilot Study of a Planted Coniferous Stand

Li,

Lin,

et al. 2024

Forests

View full text Add to dashboard Cite

show abstract

“…Laser-based distance measurement provides a simple and direct approach to high precision vibration detection [5], [6]. Recently, distance measurement based on femtosecond lasers and optical frequency combs have drawn great attention [7]- [13]. In particular, a dual-comb configuration [14]- [16] allows direct time-of-flight (TOF) absolute distance measurements with large un-ambiguous range, sub-micrometer precision, high update rate, negligible dead-zone and traceability timefrequency standard [17]- [20].…”

Section: Introductionmentioning

confidence: 99%

Singular Spectrum Analysis for Extracting Low Amplitude Vibrations in Femtosecond Laser Time-of-Flight Distance Measurements

Cao

Song

et al. 2021

IEEE Photonics J.

View full text Add to dashboard Cite

We utilize singular spectrum analysis (SSA) for post-processing distance measurement data obtained by a dual-comb femtosecond laser rangefinder. Signal denoising technique based on SSA allows detection of low amplitude vibrations from time series of distance data with limited signalto-noise ratio (SNR). Various one-dimensional vibrations, including harmonic, amplitude modulated harmonic, and sinc-function vibrations, with micrometer amplitude comparable with measurement uncertainty of laser rangefinder, have been imposed on the target mirror by a piezo positioner. These vibrations have been extracted by SSA and the obtained vibration amplitudes agree with that imposed on the target very well. A commercial interferometer is used to evaluate the accuracy of SSA. Standard deviations of residuals between the SSA extractions and interferometer measurements are smaller than 0.6 µm. This technique is promising for complex moving pattern detection in object tracking and remote sensing.

show abstract

“…Frequency-shifted feedback loops (FSL) have attracted much attention recently because their peculiar time-frequency properties could lead to numerous applications, such as ultra-high repetition rate pulse generation [1], frequency-to-time mapping [2], optical signal processing [3], arbitrary waveform generation [4,5], heterodyne spectroscopy [6], and ranging [7,8,9]. Inspired from frequency-shifted feedback (FSF) lasers [10,11], a frequency-shifting loop is a sub-threshold ring resonator.…”

Section: Introductionmentioning

confidence: 99%

Analysis of frequency-shifting loops in integer and fractional Talbot conditions: electro-optic versus acousto-optic modulation

et al. 2020

Self Cite

View full text Add to dashboard Cite

Frequency-shifting loops (FSL) are analyzed theoretically in cases where the intracavity modulator induces two side-bands at each round-trip, a situation that can be commonly obtained with electro-optic intensity or phase modulators. Using a simple model, we discuss the ability of such loops to perform frequency-to-time mapping, in the integer Talbot condition, or pulse repetition rate enhancement, in the fractional Talbot condition. The results are compared to the established acousto-optic FSL with pure frequency shift. We show that, in spite of a more complicated situation resulting from the dual sideband modulation, pulse repetition rate amplification can be obtained with an amplitude modulator, and frequency-to-time mapping can be obtained with a phase modulator. This opens new routes to high-frequency manipulation of microwave-optical signals with high-bandwidth (multi-GHz) modulators.

show abstract

A novel hybrid TOF/phase-shift method for absolute distance measurement using a falling-edge RF-modulated pulsed laser

Cited by 7 publications

References 21 publications

Effects of Illumination Conditions on Individual Tree Height Extraction Using UAV LiDAR: Pilot Study of a Planted Coniferous Stand

Effects of Illumination Conditions on Individual Tree Height Extraction Using UAV LiDAR: Pilot Study of a Planted Coniferous Stand

Singular Spectrum Analysis for Extracting Low Amplitude Vibrations in Femtosecond Laser Time-of-Flight Distance Measurements

Analysis of frequency-shifting loops in integer and fractional Talbot conditions: electro-optic versus acousto-optic modulation

Contact Info

Product

Resources

About