查看更多>>摘要：InGaN-based light-emitting diode(LED) as for the replacement of conventional fluorescent lighting source still needs a great effort to improve the light-extracting efficiency as well as internal quantum efficiency of LEDs. Surface plasmon technology has recently attracted considerable interest, because the spontaneous emission rate and the light extraction efficiency of a light-emitting device can be simultaneously enhanced through the coupling between an InGaN quantum well and surface plasmons. The surface plasmon-emitter coupling technique would lead to high brightness multichip white LEDs that offer realistic alternatives to conventional fluorescent light sources. In this article, the possible enhancement mechanism of surface plasmon is discussed, and then recent developments of surface-plasmon-enhanced light-emitting diode are introduced.
查看更多>>摘要：In order to detect and recognize infrared target with joint transform eorrelator, a modified Cassegrain optical system is designed. The main advantages of the system are large field-of-view, infrared dual-hand common optical path and compact structure. In the modified Cassegrain optical system, the working wavelengths are. 3.7～4.8 μm and 8～12 μm, the field-of-view is 4° and the aperture is 240 mm. The paraholoidal primary mirror and hyperboloidal secondary mirror are all replaced by spherical surfaces. So the problems of high machining accuracy and alignment become much easier. In order to balance the aberrations, three compensating lenses are used in the system. The total length of the system is 183 mm, and the ratio of the total length to focal length is 0.68. Moreover, the system has a good performance of athermalization between negative 40 ℃ and positive 60 ℃. The design results of the system show that the MTF value of each field is greater than 0.72 when the cut-off frequency is 11 1p/mm. Due to the excellent image quality of the modified optical system, the ability of Joint transform correlator (JTC) applied in target tracking and identification has been improved for further.
查看更多>>摘要：Light propagation in nanoparticle-loaded encapsulants is simulated based on the method of Monte Carlo, referring to the muhilayer graded-refractive-index structure for LED encapsulants. And the influence of scattering coefficient on the transmittance is analyzed. The results show that the transmittance decreases with scattering coefficient. For a given number of layers, the encapsulants will yield maximum transmittance if the refractive index value of each layer is optimized. The nanoparticle-loaded encapsulant consists of multiple layers with refractive-index values that gradually decrease. The transmittance will be higher than that of traditional non-graded encapsulants, and will improve light extraction efficiency of LED.
查看更多>>摘要：Speed sign detection and recognition are the important part of the driving assistant systems. Combining gradient-based random Hough transform with BP network, a method is proposed to detect and recognize speed signs. Firstly, the gradient-based random Hough transform is used to detect and locate the speed signs. Then four contour features of the 'digit' inside the speed signs are extracted and recognized using the method of BP network. The results show that this method can detect and recognize the speed signs accurately and efficiently.
查看更多>>摘要：The wedge-shaped and leaf-type silicon light-emitting devices(LED) are designed and fabricated with the Singapore Chartered Semi Inc. 's dual-gate standard 0.35 μm CMOS process. The basic structure of the two devices is N well-P+ junction. P+ area is the wedge-shaped structure, which is embedded in N well. The leaf-type silicon LED device is a combination of the three wedge-shaped LED devices. The main difference between the two devices is their different electrode distribution, which is mainly in order to analyze the application of electric field confinement(EFC). The devices' micrographs were measured with the Olympus IC test microscope. The forward and reverse bias electrical characteristics of the devices were tested. Light measurements of the devices show that the electrode layout is very important when the electric field confinement is applied.
查看更多>>摘要：Heat management is one of the burning questions for the spreading of LED lighting, one solution for which is to design radiators reasonably. In this article, a radiator sold on the market was modeled on ANSYS using APDL and an optimum radiator structure was achieved by making use of the optimization function of ANSYS. The radiator efficiency was increased by optimizing several parameters simultaneously. Experimental results indicate that the volume of the optimum radiator is decreased to 75.79% of that of the initial model with the junction temperature remaining at the primary level, which saves a considerable amount of material with higher radiant efficiency.
查看更多>>摘要：A silicon-based PIN photodetector structure with the characteristics of high responsibility and high cut-off frequency fabricated with the PERL (the passivated emitter and the rear locally-diffused) technologies is introduced in this paper. After making some tiny adjustments of the structure, Silvaco software is used to simulate three similar structures of PIN photodetector by measuring the spectral response, dark current, cut-off frequency and dc characteristics. From the results, it is concluded that PIN photodetector with the middle shallow diffusion area is superior to the other two ones in dark current, at least 35% lower. The responsibility of these three kinds of detector reaches the degree of 0.3 A/W, and the highest spectral response is around 600 nm. Their cut-off frequencies are all over 108 Hz.
查看更多>>摘要：A diode-pumped doubly Q-switched Nd : YAG laser operating at 1 064 nm both with an acoustic-optical(AO) modulator and Cr4+ : YAG saturable absorber in the cavity is demonstrated. At the incident pump power of 11.8 W the laser can generate stable 8ns pulse with the peak power of 23.6 kW at a 10 kHz repetition rate. The pulse temporal profile is more symmetric and shorter compared with that of passively Q-switched lasers with only AO-active and Cr4+ : YAG. A reasonable analysis is developed to explain the experimental results theoretically.
查看更多>>摘要：In order to meet the requirements of medical research, diagnosis and treatment, a new algorithm for image fusion based on the wavelet packet transform in conjunction with both subjective and objective assessments is put forward in the paper. Compared to the wavelet transform, the wavelet packet transform is more intricate and effective for the medical image fusion. As indicated by the experimental results, parameters of the feedback system of the new algorithm are significantly superior to those of the wavelet transform, with practicability and accuracy.
查看更多>>摘要：Agilent 33200A family of function/arbitrary waveform generators are widely used in labs for creating arbitrary waveforms. Flexible applications of function/arbitrary waveform generator 33250A which is made by Agilent company are expatiated. There are three methods of transferring waveform data to arbitrary waveform generator 33250A, among which, the front panel method can produce a simple interfaee for arbitrary waveforms and is applicable to the composition of a small amount of linear waveform segment, and the progress of this method is explained in detail. This way is convenient and can be widely used, and it will offer some good guidance in library works.
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