The receiver dead time is determined by the photon detector’s dead time and the response time interval of its related processing circuit in photon counting lidar. In this paper, the influence of dead time of single pixel and multi-pixel detector on the aperture of receiving lens, ranging error and ranging accuracy is analyzed in detail. From the simulation results, different sizes of receiving lens aperture were selected for detectors with different dead time effects to match the final measurement accuracy. The multi-detector array and multi-channel signal preprocessing circuit can be used to realize independent preprocessing of each detection channel to obtain time mark data of each photon event, and then all data can be processed uniformly based on histogram statistics. With the above two methods, the noise counts of each detected pixel can be significantly reduced, and the dead time effect of each channel can be suppressed. Most importantly, he time-domain drift and ranging error of echo photons can be effectively reduced. Compared with the single pixel, the multi-pixel detector can greatly increase the maximum allowable receiving area, reduce the demand for single pulse energy of the transmitter, and facilitate the engineering implementation.
A resonantly pumped monolithic Ho:YAG nonplanar ring oscillator (NPRO) with single-frequency and dual-wavelength laser outputs is demonstrated. The Ho:YAG NPRO is resonantly pumped by a 1907-nm Tm:YLF laser. In single-frequency operation, the output power is 3.09 W, with a slope efficiency of 61% and an optical efficiency of 48% with respect to the pump power. Up to 10 W dual-wavelength laser output at 2091 and 2097 nm is also obtained from the Ho:YAG NPRO with the maximum pump power, with a slope efficiency of 61% with respect to the pump power.
In self-powered wireless sensor nodes, the efficiency for environmental energy harvesting, storage and
management determines the lifetime and environmental adaptability of the sensor nodes. However, the method of
improving output efficiency for traditional photovoltaic power generation is not suitable for a solar micro-power
system due to the special requirements for its application. This paper presents a solar micro-power system
designed for a solar self-powered wireless sensor node. The Maximum Power Point Tracking (MPPT) of solar
cells and energy storage are realized by the hybrid energy storage structure and "window" control. Meanwhile, the
mathematical model of energy harvesting, storing and management is formulated. In the novel system, the output
conversion efficiency of solar cells is 12%.
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