Optical Intensity Far-Field Distribution of MEMS Micro-mirror Arrays by Fraunhofer Diffraction

Compared with liquid crystal clad waveguide, MEMS mirror has some merits, such as high-er-transmissivity, lager-angle of scanning, faster scanning speed and so on. Furthermore, MEMS mirror arrays perform more superior than MEMS mirror when they steer laser beam, which make MEMS arrays much more suitable to be used in devising compact Lidar. Before assembling a Lidar with MEMS arrays, the optical intensity and distributions of the laser diffracted by MEMS arrays should be analyzed, but few published papers about this issue are available so far, this paper will focus on this issue about MEMS arrays. Firstly, the complex amplitudes of laser which is diffracted by 1-D and 2-D arrays are presented, respectively. Then the optical intensity and distributions on the observation plane are presented. Finally, the simulation diagrams of these distributions are shown, and the correctness of the results is indirectly verified by Young’s dou-ble-slit experiment. The results gotten in this letter are essential to design a compacted Lidar based on MEMS arrays.

Implementasi Automatic Dependent Surveillance Broadcast (ADS-B) di Indonesia

Teknlologi ADSB is a new technology in the observation plane which is a combination of global positioning system (GPS), so that the aircraft can be traced to the position, velocity, wind direction, and altitude. This tool can be installed in the aircraft or ground stations and more superior than the radar.ADS-B is indeed a revolutionary look, start with only the antenna and the tool less than for a small refrigerator can detect aircraft and air traffic displays.Automatic Dependent Surveillance- Broadcast (ADS-B) is a detection technology where each plane passing owned transponder emits every two times per second information altitude, position, speed, direction, and other information to ground stations and other aircraft. This information is obtained from the information the Global Positioning System (GPS) or backup Flight Management System (FMS) in each plane. Teknlologi ADSB adalah teknologi baru dalam pengamatan pesawat terbang yang merupakan kombinasi global positioning system (GPS), sehingga pesawat bisa terlacak posisi, kecepatan, arah angin, dan ketinggian. Alat ini bisa dipasang di pesawat atau stasiun darat dan lebih unggul dari radar. ADS-B ini memang terlihat revolusioner, dengan hanya berbekal antenna dan alat kurang dari sebesar lemari es kecil dapat mendeteksi pesawat terbang dan menampilkan lalu lintas udara.Automatic Dependent Surveillance- Broadcast (ADS-B) adalah teknologi pendeteksi dimana setiap pesawat lewat transponder yang dimiliki memancarkan setiap dua kali dalam tiap detik informasi ketinggian, posisi, kecepatan, arah, dan informasi lainnya ke stasiun darat dan pesawat lainnya. Informasi ini didapat dari informasi Global Positioning System (GPS) atau backup Flight Management System (FMS) yang ada di pesawat masing-masing.

Extensions of Electron Diffraction Based Techniques in Crystallographic Characterization

With the advance of electron diffraction techniques in individual orientation analysis, traditional crystallographic characterization methods could be simplified, thus offering chances to develop some new approaches. In recent years, our group has devoted to working on possible extensions of the SEM and TEM based techniques for crystallographic analyses on a microstructure- and orientation-specific level. Several methods are illustrated in this paper, including the determination of dislocation type and Burgers vector without recourse to the traditional g.b invisibility condition, the identification of twinning mode and complete twinning elements for any crystal symmetry that requires minimum initial data input, and the characterization of specific interface plane or slip plane using only one sample observation plane instead of two perpendicular sample planes. These new extensions of characterization methods have proven to facilitate the related microstructural examinations.

Influence of the Brownian movement on the motion of nanoand micro-particles in the inhomogeneous optical field

The motion of light scattering particles of the Mie and Rayleigh micro- and nano-range type in the inhomogeneously-polarized optical field, with allowance made for the Brownian movement, is analysed in the paper. The spatial modulation of polarization in the observation plane determines the spatial modulation of the volume energy density. That is why the velocity and the resulting optical force, which cause the motion of the testing particles, change according to the degree of coherence of the interacting fields. The influence of the forces which arise in the viscous medium and cause the Brownian movement upon the mechanisms of manipulating and trapping testing particles by the optical field is studied.

Dual-Doppler Analysis in a Single Plane from an Airborne Platform

A modified dual-Doppler analysis technique for use with airborne Doppler radars utilizing two fixed beams is presented. Although the data collected by such a system would ideally lie in the plane defined by the radar beam orientations and the aircraft velocity vector, variations in the aircraft attitude and drift angles lead to displacements between the radar observations and the idealized observation plane. These variations motivated the development of a formal framework in which an a priori velocity estimate is used in conjunction with the two Doppler velocity measurements to form a three-dimensional velocity estimate. Two velocity components, lying within or close to the observation plane, and therefore containing only a small contribution from the a priori velocity estimate, are then extracted from the three-dimensional velocity estimate. Advantages of using the three-dimensional framework include improved accuracy (when an a priori velocity estimate is available) and a framework for assessing the effects of cross-plane contamination on the retrieved velocity components. The velocity fields retrieved using the modified dual-Doppler analysis are affected by errors in the platform motion correction to the Doppler velocities, random noise in the mean Doppler velocity estimates, displacements between the radar beams (and between the radar beams and the idealized observation plane), and meteorological velocity variations about the a priori velocity estimate. Errors in the platform motion correction remain poorly characterized but are believed to be the largest source of error in many cases. However, these errors result primarily in biases (or low-frequency errors) in the retrieved velocity fields and therefore do not interfere with the ability to resolve actual velocity variations. Random noise in the mean Doppler velocity estimates increases dramatically with decreasing signal-to-noise ratio (SNR) (for SNR < 5 dB) and effectively limits the use of the single-plane dual-Doppler (SPDD) analysis to SNR > 0 dB. Displacements between the volumes sampled by the nadir and slanted beams can also be a significant source of error, especially at larger displacements from the aircraft. Errors resulting from meteorological velocity variations about the a priori velocity estimate tend to be small compared to the velocity variations of interest. The dual-Doppler analysis presented in this paper has been applied to retrieve two-dimensional velocity fields with a resolution of ∼50 m using Doppler velocities collected using dual-beam configurations of the Wyoming Cloud Radar. Results are in horizontal and vertical planes for marine stratocumulus, cumulus congestus, and for the clear-air boundary layer.