The streak tube imaging LiDAR has promising application prospect due to the ability of full waveform sampling and high sensitivity. This kind of LiDAR generates massive point cloud data with high efficiency. However, the distribution of laser foot points is found usually irregular due to the scanning mode of this kind of LiDAR. This paper focuses on the interpolation of ideal points to realize uniform distribution of the point cloud using interpolation techniques, including nearest neighbor, arithmetic mean and inverse distance weighted interpolation. Specifically, we propose a new homogenization method in which the inverse distance weighted interpolation is improved. The suitability of homogenization methods for point cloud generated by streak tube imaging LiDAR is tested. The results show that the nearest neighbor method has better restoration of buildings with abrupt elevation values and inverse distance weighted interpolation outperforms other selected methods when processing flatland. It has been proven that the new method we propose possesses the advantages of both nearest neighbor and inverse distance weighted techniques.
Waveform sampling LiDAR is a hot topic in LiDAR technique due to its high precision geodesy and multi-layer target detection ability. Especially, the LiDAR systems applying streak tube have encouraging application due to their special properties about high-sensitivity and full waveform sampling ability. This paper describes a kind of LiDAR system applying the full waveform sampling stripe principle array. Basing on the planar fitting of square object, the elevation error of points cloud got from flight experiment is analyzed. The statistical properties of elevation error are got.
Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy is utilized to measure the premixed
methane/oxygen/nitrogen flame temperature at atmospheric-pressure. The procedure for fitting theoretical spectra to
experimental spectra is explained. The experimental results show good agreements with theoretical ones and present a
good repeatability. Laser parameters are very important for accurate temperature measurements. The effects of laser
parameters on temperature measurements are discussed. Laser parameters in our discussion are shown as follows. Laser
pulse shape is hyperbolic secant and Lorentz, respectively. The delay time between the pump and Stokes is from -40 fs to
+40 fs. The central wavelength of the pump/probe pulses is from 650 nm to 700 nm. Pulse duration is from 40 fs to 120
fs. In 2000 K, variations of delay time between the pump and Stokes pulses lead to less than 5% error and while
variations of the other three parameters lead to less than 1.5% error. Timing jitter is added to the pump/probe pulses and
Stokes pulses. In 2000 K, the results indicate that timing jitter of 10% lead to less than 2% error for temperature
measurements. In the higher temperature measurement, the impact of laser parameters’ error is greater.
Multi-photon excitation in ZnO material by femtosecond (fs) laser pulses around 800 nm was clearly observed.
Under the intense field generated by fs pulses, two-photon absorption process was found very efficient in the
excitation of the band edge emission from ZnO material under detuning condition. Nonlinear optical effects, such as
Stark effect and Rabi effect, that may emerge under intense field are suggested to be responsible for this efficient
excitation via two-photon absorption process. We consider that this NLO route to generate photoluminescence in
ZnO material is meaningful in the research of blue-violet semiconductor laser field.