JPH01292735A - Objective lens of transmission electron microscope - Google Patents

Abstract

PURPOSE:To make it possible to obtain an electron microscope image full of variety by making the structure of the objective lens of a transmission electron microscope in the title to have a rear focal surface formed near the top plane of the lower pole of the lens and arranging an orifice near the rear focal surface. CONSTITUTION:A transmission electron microscope is composed of an electron gun 8, a lens system 1, an image observation chamber 2 and a camera chamber 3, while an objective lens 10 is composed of an upper pole 11 and a lower pole 12. A sample 13 and an objective stop 14 are also arranged between the upper pole 11 and the lower pole 12. Moreover, the objective lens 10 is designed to have a rear focal surface formed underneath the objective stop 14, with an orifice 4 arranged near the rear focal surface. Thus, the excitation of a projection lens can be freely changed, and an electron microscope image full of variety can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an objective lens for a transmission electron microscope, and in particular,
This invention relates to an objective lens for a transmission electron microscope that has an orifice that separates the degree of vacuum.

[Prior Art] As shown in FIG. 2, a transmission electron microscope is comprised of an electron gun 8, a lens system 1, an image observation chamber 2, and a camera chamber 3.

The lens system 1 consists of an irradiation lens system in front of the sample and an imaging lens system behind the sample, and the image observation chamber 2 has a fluorescent screen,
This is the part where the electron microscope image is visualized and observed by irradiating the fluorescent screen with the electron beam that has passed through the imaging lens system. Further, a photographic film is stored in the camera room 3, so that an electron microscope image can be photographed as needed.

By the way, since photographic film contains moisture, it is difficult to maintain the camera room 3 in a highly vacuum state, and normally
Only about 0"mmHg can be obtained. On the other hand, the sample must be placed in a high vacuum region of 10"mmHg or more. This is because the sample will be contaminated if the vacuum is poor. For this purpose, as shown in FIG. 2, an orifice 4 is provided to separate the part where the sample is placed from the vacuum area of the camera chamber 3. This takes advantage of the property that in a relatively high vacuum region called the molecular flow region, gases separated by small openings, or orifices, have very little chance of mixing and maintain their respective states.

Therefore, the question becomes where to arrange the orifice 4. The diameter of the opening of the orifice 4 is usually about 0°3 mm.
Because it has to last for about one night at most, it is necessary to place the lens 5 on the back focal plane as shown in Fig. 3. The condition is to not move much and to stay still. These conditions are most easily met at the back focal plane directly below the projection lens, so conventionally the orifice 4 is placed directly below the projection lens pole piece.

[Problems to be Solved by the Invention] However, in the conventional transmission electron microscope, the orifice 4 is disposed directly below the projection lens pole piece, so a problem arises in that the excitation of the projection lens is restricted. In other words, a projection lens can project a wide variety of electron microscope images onto a fluorescent screen or photographic film by changing its excitation, so it is a useful lens that can be used for a very wide range of purposes. As mentioned above, due to the existence of the orifice 4, the excitation is almost fixed, and even if it is changed, it can only be changed very slightly, so the magnification cannot be changed arbitrarily, and there is a restriction that it is not possible to obtain a wide variety of electron microscope images. Ta.

In this way, the possibilities of the projection lens are utilized (the presence of the orifice 4 above was a major obstacle).

The present invention solves the above-mentioned problems, and is a transmission electron microscope capable of obtaining a wide variety of electron microscope images by freely changing the intensity of excitation of the projection lens. The object of the present invention is to provide an objective lens.

[Means for Solving the Problems] In order to achieve the above object, the objective lens of the transmission electron microscope of the present invention has a structure in which the focal plane is formed near the bottom top surface of the lens, and the back focal plane It is characterized by an orifice placed nearby.

[Function] In the present invention, the objective lens has a structure in which the focal plane is formed near the bottom top surface of the lens, and the orifice is arranged near the back focal plane, so that the sample is placed in a highly vacuum region. Of course, since the projection lens is no longer subject to the conventional restrictions, the excitation can be changed arbitrarily and its performance can be fully demonstrated.

[Example code] Examples will be described below with reference to the drawings.

FIG. 1 shows one of the objective lenses of a transmission electron microscope according to the present invention.
FIG. 2 is a diagram showing the configuration of an example, in which an objective lens 10 is composed of an upper pole 11 and a lower pole 12, and a sample 13 and an objective aperture 14 are arranged between the upper pole 11 and the lower pole 12. In addition,
The objective aperture 14 blocks high-order reflections to improve image contrast, or cuts off the electron beams that have passed through without being scattered, creating an image (dark-field image) using only the scattered electron beams.
It is used to make.

In the configuration shown in FIG. 1, the objective lens 10 is an objective aperture 1.
4, the orifice 4 can be placed near the back focal plane. Note that, as shown in FIG. 1, it is possible to form the back focal plane directly below the objective aperture 14 depending on the shape of the pole piece. In addition, in Fig. 1, the orifice 4
and the diameter of the objective aperture 14 are, for example, 0.31
(2) It can be set to 0.05 degrees.

If the back focal plane is formed in the objective lens pole piece as shown in FIG.
If the orifice 4 is formed under the pole pieces 4 and above the top surface of the lower pole 12, the orifice 4 may be provided as a bridge between the pole pieces.

Since the orifice 4 is originally provided only to maintain the sample chamber in a high vacuum region, the configuration shown in FIG. 1 can also achieve this purpose. However, although the excitation of the objective lens 10 is varied for focus adjustment, it is only a small amount, so the position of the back focal plane hardly moves, and the orifice 4 functions effectively.

In the configuration shown in FIG. 1, it is desirable to arrange the objective diaphragm 14 as close to the orifice 4 as possible. However, the fact that the objective aperture 14 is not located at the back focal plane does not impair the performance of a normal transmission electron microscope.

[Effects of the Invention] As is clear from the above description, according to the present invention, by providing an orifice, the sample chamber can be kept in a highly vacuum region, and the orifice can be placed in the rear focal plane of the objective lens. Since they are placed nearby, the excitation of the projection lens can be changed freely, making it possible to obtain a wide variety of electron microscope images.

[Brief explanation of the drawing]

FIG. 1 shows one of the objective lenses of a transmission electron microscope according to the present invention.
FIG. 2 is a diagram showing the configuration of a conventional transmission electron microscope, and FIG. 3 is a diagram illustrating the arrangement of orifices. 1... Lens barrel, 2... Image observation room, 3... Camera room,
4... Orifice, 8... Electron gun, 10... Objective lens, 11... Upper pole, 12... Lower pole, 13...
Sample, 14...Objective aperture. Figure 1

Claims (1)

[Claims] (1) An objective lens for a transmission electron microscope whose rear focal plane is formed near the lower top surface of the lens, characterized in that an orifice is disposed near the rear focal plane.