Design of infrared optical system based on three germanium lens with low stray radiation

Author(s):  
Zeyao Cui ◽  
Zhifeng Pan ◽  
Weifeng Ren ◽  
Chenjie Jin ◽  
Xin Yu
2019 ◽  
Vol 48 (9) ◽  
pp. 904006
Author(s):  
张发强 Zhang Faqiang ◽  
张维光 Zhang Weiguang ◽  
万文博 Wan Wenbo

2019 ◽  
Vol 40 (1) ◽  
pp. 1-8
Author(s):  
HAN Xing ◽  
WU Hanxiao ◽  
WANG Longyi

2017 ◽  
Vol 46 (1) ◽  
pp. 120004
Author(s):  
游兴海 You Xinghai ◽  
胡小川 Hu Xiaochuan ◽  
彭家琪 Peng Jiaqi ◽  
张彬 Zhang Bin

2016 ◽  
Author(s):  
Yang Li ◽  
Tingcheng Zhang ◽  
Zhibo Liao ◽  
Shengbo Mu ◽  
Jianxiang Du ◽  
...  

2017 ◽  
Vol 46 (1) ◽  
pp. 120004
Author(s):  
游兴海 You Xinghai ◽  
胡小川 Hu Xiaochuan ◽  
彭家琪 Peng Jiaqi ◽  
张彬 Zhang Bin

Author(s):  
Michel Troyonal ◽  
Huei Pei Kuoal ◽  
Benjamin M. Siegelal

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).


Author(s):  
B. Roy Frieden

Despite the skill and determination of electro-optical system designers, the images acquired using their best designs often suffer from blur and noise. The aim of an “image enhancer” such as myself is to improve these poor images, usually by digital means, such that they better resemble the true, “optical object,” input to the system. This problem is notoriously “ill-posed,” i.e. any direct approach at inversion of the image data suffers strongly from the presence of even a small amount of noise in the data. In fact, the fluctuations engendered in neighboring output values tend to be strongly negative-correlated, so that the output spatially oscillates up and down, with large amplitude, about the true object. What can be done about this situation? As we shall see, various concepts taken from statistical communication theory have proven to be of real use in attacking this problem. We offer below a brief summary of these concepts.


Author(s):  
J T Fourie

The attempts at improvement of electron optical systems to date, have largely been directed towards the design aspect of magnetic lenses and towards the establishment of ideal lens combinations. In the present work the emphasis has been placed on the utilization of a unique three-dimensional crystal objective aperture within a standard electron optical system with the aim to reduce the spherical aberration without introducing diffraction effects. A brief summary of this work together with a description of results obtained recently, will be given.The concept of utilizing a crystal as aperture in an electron optical system was introduced by Fourie who employed a {111} crystal foil as a collector aperture, by mounting the sample directly on top of the foil and in intimate contact with the foil. In the present work the sample was mounted on the bottom of the foil so that the crystal would function as an objective or probe forming aperture. The transmission function of such a crystal aperture depends on the thickness, t, and the orientation of the foil. The expression for calculating the transmission function was derived by Hashimoto, Howie and Whelan on the basis of the electron equivalent of the Borrmann anomalous absorption effect in crystals. In Fig. 1 the functions for a g220 diffraction vector and t = 0.53 and 1.0 μm are shown. Here n= Θ‒ΘB, where Θ is the angle between the incident ray and the (hkl) planes, and ΘB is the Bragg angle.


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