Material contrast in SEM: Fermi energy and work function effects

‘Is it possible to assign various grey levels of a scanning electron microscope (SEM) image to different components of a given sample? Among other instrumental effects, the answer is not only a function of the respective secondary electron emission (SEE) yields of the components, δ, but also of the angular fraction of the secondary electrons (SE)s being collected, k_α and of a possible voltage contact effect between sample and detector, k_?. Expressed as a function of E_F, Fermi energy, and ?, work function of the components of interest, equations of spectral, (∂δ/∂E_k), and angular, (∂δ/∂α) distributions of the emitted SEs permit to evaluate k_α and k_? for Au and Si. It has been established that collected SE spectra, ∂δ_α/∂E_k, are distorted with respect to the emitted and fraction k_α is material dependent for a solid angle of detection Ω° less than 2π (or maximum semi-apex angle α_max<90°) In particular, for coaxial detections around the normal incident beam the detected fraction of SEs from Au, k_α(Au), is slightly larger than that for Si, k_α(Si). For simple geometries in the vacuum gap, similar investigations show that parameter k_φ is also larger for gold than for n-doped Si as well as for p-doped Si with respect to n-doped Si. Then Au is always quite brighter than n-doped Si in the SEM images while a doping contrast, C, due to a work function effect may reach ∼15% for a Si p/n junction with N_p∼10¹⁶ and N_n∼10¹⁵ cm⁻³. The present analysis may be extended to some metals such as Ag, Cu, Pb, Pd, Pt, and Zn that are expected to appear brighter than Si(n) and Ge in the SEM images.     

图像测量系统中的误差分析及提高测量精度的途径

为了进一步提高图像测量系统的测量精度,必需考虑影响测量精度的诸多因素,如:照明视场噪声、热电子噪声、CCD性能、镜头畸变、量化误差、帧存与CCD不同步、温度、振动、视频馈线等的影响。本文将分析这些误差对图像测量系统测量精度的影响,并给出消除或减小误差的有效方法,从而提高测量精度     

显微虫卵微机自动检测装置及虫卵快速检测算法

本文简要介绍了显微虫卵微机自动检测装置的硬件设计。详细介绍了基于该装置的绦虫卵快速检测算法。该算法根据绦虫卵图象特点，将传统目标检测步骤有机地融合在一起，使预处理和检测一次完成。在无虫卵情况下可快速扫描图象，提高了检测速度，同时也提高了检测率。实验结果证实了这些效果     

物面、像面、主面交于一线原理的证明及应用

通常光学成像系统,物面、像面及成像物镜与光轴都是垂直的,在特殊光学系统中,比如宇航模拟中的视景模拟光学系统,物面是倾斜的(即不垂直于光轴),造成像的不清晰。本文为使倾斜物面也能成一清晰的象,而引出了物面、像面、镜组主面交于一线的原理,并从几个方面对这个原理加以证明。在文中应用此原理推导出了单组、双组物镜组校正像面倾斜的关系式,编制了用镜组倾斜校正像面倾斜实时控制程序。     

激光致熔池图像获取及质心提取方法研究

激光焊接已广泛应用于航空航天、汽车、船舶、医疗器械等领域关键部件的制造。为保证焊接质量,可使用工业CCD相机在焊接过程中实时检测熔池中心与焊缝间的偏差,并根据偏差进行调整。因此,首先要对激光致熔池获取和质心提取方法进行研究。由于激光焊接中熔池温度高,应用工业CCD相机直接拍摄熔池的图像无法进行图像处理。为拍摄熔池清晰图像,在对熔池辐射光线特性进行分析的基础上,结合工业CCD光谱响应特性,确定合适的采集熔池图像所需光谱波长范围。应用镜头前放置了所求波长滤光片的工业CCD相机,拍摄直接作用在304钢板上的激光致熔池图像,并对熔池边缘识别和熔池质心计算方法进行了研究。实验表明,所提出激光致熔池提取方法及质心计算方法有效。     

Scale effects and a method for similarity evaluation in micro electrical discharge machining

Electrical discharge machining(EDM) is a promising non-traditional micro machining technology that offers a vast array of applications in the manufacturing industry. However, scale effects occur when machining at the micro-scale, which can make it difficult to predict and optimize the machining performances of micro EDM. A new concept of “scale effects” in micro EDM is proposed, the scale effects can reveal the difference in machining performances between micro EDM and conventional macro EDM. Similarity theory is presented to evaluate the scale effects in micro EDM. Single factor experiments are conducted and the experimental results are analyzed by discussing the similarity difference and similarity precision. The results show that the output results of scale effects in micro EDM do not change linearly with discharge parameters. The values of similarity precision of machining time significantly increase when scaling-down the capacitance or open-circuit voltage. It is indicated that the lower the scale of the discharge parameter, the greater the deviation of non-geometrical similarity degree over geometrical similarity degree, which means that the micro EDM system with lower discharge energy experiences more scale effects. The largest similarity difference is 5.34 while the largest similarity precision can be as high as 114.03. It is suggested that the similarity precision is more effective in reflecting the scale effects and their fluctuation than similarity difference. Consequently, similarity theory is suitable for evaluating the scale effects in micro EDM. This proposed research offers engineering values for optimizing the machining parameters and improving the machining performances of micro EDM.