3D detection is an important application of Lidar. A 3D range imaging Lidar system is presented in this paper. The
longitudinal resolution of 3D range imaging Lidar is poor because of the length of pulse width and gate time of ICCD,
which together determine the detected longitudinal range from a single laser pulse shot. To improve the longitudinal
resolution, power distribution received by one pixel of ICCD is analyzed, and a method is put forward. In this method,
by setting the gate time and step interval of delay time to the value of pulse width, one object will be detected in two
neighboring images, and it can be precisely located through analysis of the pixel values in the two images. The locating
precision of this method is verified by experiments, and results show that the longitudinal resolution is improved by ten
times, that is from 1.65m to about 0.15m. Meanwhile, the detection efficiency is reduced only a little.
Pure Rotational Raman Lidar is a new technique for detecting vertical troposphere temperature profile. Since the
backscattering Raman signals are so weak that the photon-counting method is applied by using a multiscaler. By setting
the threshold of the multiscaler, most noises mixed with the signals can be filtered. However, difference exists between
the set threshold and the actual threshold of the two count channels, and also exists between the set thresholds of the two
count channels. This will affect quick-setting of the appropriate thresholds. In this paper, a rule is put forward and the
measuring system is established to confirm the set threshold value corresponding to an actual one, making use of the
amplitude fluctuation of square wave. By this system, pairs of set threshold and actual threshold are obtained, and the
curve of the set threshold against the actual threshold of a single count channel, as well as the curve of thresholds of the
two count channels, is fitted. The theoretical analysis is well agreed with the experimental results, and it indicates that
the appropriate threshold can be set more quickly by using the curve.
Pure Rotational Raman Lidar is a recently developed method for atmospheric temperature detection. Since the
Raman-scattering-signals are very weak, the photon-counting method is employed, which could be achieved by using a
multiscaler. Time delays, which exist among the trigger channel and the two count channels of the multiscaler, will affect
the corresponding relationship between the detected signals and the actual altitudes where the signals are returned, so it
is necessary to make some compensation. However, it is difficult to measure the time delays with traditional instruments
such as oscillograph, for there is no access to the final internal trigger signal or count signals. In this paper, a measuring
system is established, with a Digital Delay/Pulse Generator as the chief component, which is not usually used as a
measuring instrument. The measurement precision could reach about 50ps. Meanwhile, the compensating method is also
provided to improve the positioning accuracy of the lidar system.
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