Condenser lenses are most useful at the highest powers (400X and above). In microscopy, lenses are often used to demagnify (make smaller) the diameter of the beam. In this case it is more appropriate to draw the ray diagram. The double condenser system or illumination system consists of two or more lenses and an aperture.

透射式电子显微镜 （TEM）的工作原理与投射式光学显微镜很相似，图1画出了两者的简化光路图，尽管光源、透镜各不相同，但照放大及成像方式却完全一致。 图1 投射光镜与透射电镜的光路对照图. 在实际情况下无论是光镜还是电镜，其内部结构都要比图示复杂得多，图中的 聚光镜 （condonser lens）、 物镜 （object lens）和 投影镜 （projection lens）为光路中的主要透镜，实际制作中它们往往各是一组（多块透镜构成），在设计电镜时为达到所需的放大率、减少畸变 …

2022年5月19日 · The TEM uses two condenser lenses to converge the beam of electrons to the specimen. The two condenser lens each function to produce an image i.e the first lens which has strong magnification, produces a smaller image of the specimen, to the second condenser lens, directing the image to the objectives.

• Lens aberrations (e.g. Cs, Cc): can be corrected by multipole lenses or focus-series reconstruction • Instabilities (e.g. HT, electronic, mechanical / acoustic,

The objective lens is the most important lens in the whole microscope. All the lenses below the specimen serve to magnify the image of the specimen. Lets just think about the ray diagram shown below.

In the traditional TEM mode, the first two condenser lenses (C1, C2) are adjusted to illuminate the specimen with a parallel beam of electrons, typically several micrometers across at reasonable magnifications (20,000 –100,000 ). As shown in Figure 9.1, the C1 lens first forms an image of the gun crossover. In

Principles of TEM Operation: 1. When you want to look at the diffraction pattern (i.e., the back focal plane of the objective lens), you put an SAD aperture into the image plane of the objective lens. 2. When you want to view an image (i.e., the image plane of the objective lens), you insert an aperture into the

In most modern, practical TEMs/STEMs, the gun lens is used to position the first crossover in relation to the beam-defining aperture (normally the C2 aperture). The crossover locates high above the aperture with a strong gun lens, while the crossover is close to the aperture with a …

Typical objective lens in conventional TEMs. For an ideal objective lens, the incident electron probe simply forms an Airy disc in the back focal plane of the lens. This disc is the Fourier transform of the uniformly illuminated condenser aperture. …

Objective is the most important lens in a TEM, it has a very high field (up to 2 T) The Specimen is completely immersed in its field so that pre-field and post field can be distinguished