Aiming at the design requirement of miniature reflective optical system,a new type of off-axis three-mirror anastigmat (TMA) and freeform surface are adopted, the F#1.8,and diagonal field of view7.5° is realized.Light overlap many times within the optical system,the full field average RMS Wavefront abberations is 0.017λ(λ=10μm). Compared with other optical system, the new freeform TMA has small size, high transmittance, large field of view, large relative aperture, no centered obscuration, low stray, radiation, wide spectral band, etc.
Laser Rayleigh-Brillouin scattering is an effective non-intrusive method for measurement of density, temperature and pressure in gas flows. In theory, the power of Rayleigh-Brillouin scattered laser light is proportional to the gas density, the full width at half maximum (FWHM) and the Brillouin shift of the Rayleigh-Brillouin scattering spectrum is related to the gas temperature and pressure, respectively. In this paper, a measurement device based on Fabry-Perot interferometer (FPI) is designed to measure the Rayleigh-Brillouin spectrum of nitrogen gas. The experimental data is obtained at different pressures under room temperature conditions. The L3 model is used to fit the experimental data to obtain the FWHMs and Brillouin shifts of the Rayleigh-Brillouin profiles. The composite Rayleigh-Brillouin profiles which consist of Rayleigh peak, stokes peak and anti-stokes peak are represented by three distinct peaks of Lorentz functions. Fitting results show that the error of FWHMs and Brillouin shifts obtained by L3 model is less than 10% compare with the Tenti S6 model. Some factors that affect the measurement accuracy of the Rayleigh-Brillouin parameters are also analyzed and discussed.
KEYWORDS: Signal detection, Backscatter, Control systems, Signal processing, Clocks, LIDAR, Laser systems engineering, Pulsed laser operation, Lithium, Beam splitters
In airborne underwater lidar applications, the reflecting light signal from the sea level is stronger than the one from
the underwater object, the returned signal is decreased with the range as exponential and inverse square law and the
backscattering return is very large. So the dynamic range could reach five to six orders of magnitude in few hundreds of
nanoseconds. Therefore, it is necessary to compress the signal dynamic range to match the range of the digitizing or
processing devices, typically 2 or 3 orders of magnitude, and to eliminate the reflecting light signal from the sea level
and the backscattering. In this paper, we present a Range-Gain-Control Gated PMT method for this problem. The
principal and the design of the Range-Gain-Control Gated PMT system are analyzed and discussed. The experiment
results show that this method can complete the gated and the gain-control of the PMT.
By conducting [0, 1] treatment to time consuming of logistics system network key links, and regarding the time consumed by manufacture, inspection, storage, assembling, packing and market as a kind of existent extent of the joint and the time consumed by materials handling, transportation and logistics information as the connection strength between joints in a generalized multi-directional fuzzy map, a generalized multi-directional fuzzy map model of logistics system networks is built. The mutual flow among network joints and the special form of generalized fuzzy matrix is analyzed. Finally, an example of model building is given.
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