Limited by the number of available photons collected a pixel and stability imaging system, images captured under poor illumination conditions are often degraded heavy shot noise low contrast. In this letter, we propose novel low-light image enhancement algorithm using Poisson noise-aware Retinex model, in which distribution is considered to formulate fidelity term model for first time. Furthermore, space-variant weight maps total variation regularization terms calculated according piecewise...

As the photoelectric conversion material, semiconductor photocathode plays an important role in development of vacuum photodetectors and electron sources, efficiency stability emission have always been focus applications. Photocathode is based on external effect. Different from internal effect, photoelectrons generated by light excitation inside cathode must overcome surface barrier to escape into vacuum, so level photoemission ability closely related properties. The preparation process...

Micro pore optics including microchannel plates and lobster-eye micro-optical devices, represent milestone inventions in advanced optical engineering. High-precision fibers serve as critical components of these optics, with the quality directly determining their performance. The preparation high-precision involves two critically important processes: melting flow glass drawing process. During heating preform a high-temperature furnace, necking occurs due to gravitational tensile forces,...

针对负电子亲和势(NEA) GaN光电阴极成功激活后的量子效率问题,利用自行研制的紫外光谱响应测试仪器,测试了成功激活的NEA GaN光电阴极的光谱响应,给出了230—400 nm波段内反射模式NEA GaN光电阴极的量子效率曲线.测试结果表明:反射模式下NEA GaN光电阴极在230nm具有高达37.4%的量子效率,在GaN光电阴极阈值365 nm处仍有3.75%的量子效率,230 nm和400 nm之间的抑制比率超过2个数量级.文中还结合国外的研究结果,综合分析了影响量子效率的因素.

In view of the important application GaAs and GaN photocathodes in electron sources, differences photoemission behaviour, namely activation process quantum yield decay, between two typical types III—V compound have been investigated using a multi-information measurement system. The experiment shows that surface negative affinity state for photocathode can be achieved by necessary Cs—O two-step Cs alone photocathode. addition, decay exhibits better stability longer lifetime demountable vacuum...

We report here a general theory describing photoelectron transportation dynamics in GaAs semiconductor photocathodes. Gradient doping is incorporated the model through inclusion of directional carrier drift. The time-evolution electron concentration active layer upon injection an excitation pulse solved both numerically and analytically. predictions are compared with experiments via carrier-induced transient reflectivity change, which measured for gradient-doped uniform-doped photocathodes...

Aiming to solve the problem of low-light-level (LLL) images with dim overall brightness, uneven gray distribution, and low contrast, in this paper, we propose an effective LLL image enhancement method based on guided filter multi-scale fusion for contrast detail preservation. First, a base image(s) are obtained by using filter. After procedure, is processed maximum entropy-based Gamma correction stretch level distribution. Unlike existing methods, enhance kernel, which reflects area...

In real-time system, the Infrared Focal Plane Array (IRFPA) should be compensated in traditional method of two-point temperature non-uniformity correction (NUC) before system was used every time, which make complex. Based on discussion NUC algorithm, Two-point based least mean square (LMS) algorithm proposed paper. view LMS theory, gain and offset coefficients were iterated one by during image processing, so that expected result obtained little time. At same iteration processes completed...

A real-time color image fusion system has been presented for the infrared thermal camera and low-light-level camera, which provides more complete spectral information. The statistical transform method based on YCRCBcolor model transfers first order statistics of distribution a representative natural daytime reference to false dual -band images. This mapping is usually performed in perceptually decorrelated space. colors resulting colorized dual-band images closely resemble image. Also,...

Abstract The whole process including photoelectron excitation, transportation from bulk to surface and escape vacuum by traversing barrier was analyzed in detail. Photoelectron excitation relates the band structure of photocathode material absorption coefficient material. In GaN photocathode, photoelectrons mainly are transited into Γ valley first, when energy is great enough, can scatter higher M‐L or A valley. electrons excitated conduction will move diffusing drifting. diffuse length for...

The lifetime and reliability of a photocathode during operation are always raised problems the performance depends on vacuum condition. With purpose investigating stability GaAs-based in harsher environment, reflection-mode exponential-doped GaAs AlGaAs photocathodes metalorganic vapor-phase epitaxial grown then (Cs, O) activated inside an unbaked chamber. degraded photocurrents compared after activation recaesiations between photocathdoes under illumination with equal initial photocurrent...

Low-light images always suffer from dim overall brightness, low contrast, and dynamic ranges, thus result in image degradation. In this paper, we propose an effective method for low-light enhancement based on the just-noticeable-difference (JND) optimal contrast-tone mapping (OCTM) models. First, guided filter decomposes original into base detail images. After filtering, are processed visual masking model to enhance details effectively. At same time, brightness of is adjusted JND OCTM...

The preparation process of GaAs photocathodes is very complicated, in order to prepare the high performance cathodes, it crucial obtain information enough evaluate real time. Based on a particular transfer light setup and flexible communication network, we develop an on-line measurement system for cathode preparation, which used measure pressure activation chamber, sample temperature, photocurrent, spectral response curves, currents heating Cs oxygen dispensers during heat-cleaning or...