Scanning electron microscope assembly operating in situ

Details Scanning electron microscope assembly operating in situ Scanning electron microscope assembly operating in situ

1982-09-27

1985-05-07

Smith, Alfred E.

Radiant energy

Inspection of solids or liquids by charged particles

Electron probe type

H01J 3718, H01J 3720, H01J 3726

Patent

active

045160260

DESCRIPTION:

BRIEF SUMMARY
The present invention concerns scanning electron microscopes and, more particularly, a scanning electron microscope operating in situ.
The use of scanning electron microscope has undergone tremendous development due to their pliancy in use, notably in association with visualization cathodic screens, and to their extremely convenient performances in observation, notably concerning depth of field. These characteristics make particularly advantageous industrial use of scanning electron microscopes to check the surfaces of operational or structural elements, notably for checking manufacturing processes or the study of surface bucklings upon stress tests. To the present, the study of such surfaces has been made by conventional optical processes using magnifying glasses or optical microscopes with slight magnification and limited depth of field. Thus, it appears particularly inviting to use, for said checkings, scanning electron microscopes in view of the aforesaid stated advantages. However, as known in electron microscopy, it is required to introduce the object to be observed on a special support to place it in a vacuum plenum forming an observation chamber for the microscope. Thus, the use of electron microscopes required destructive preparation techniques requiring the taking of a sample to be placed within the observation chamber at the price of damage or buckling of the portion to be studied.
In order to obviate this disadvantage, it has been proposed to use an electron microscope observation technique using an intermediary vacuum plenum having slight sizes and connected to a powerful pumping device clearing at right angles to the portion to be observed by a diaphragm having a minute opening (of the order of 30 microns ) and a slight thickness, so as to limit the air leak output to be permanently balanced by the pumping device. The so proposed technique has a number of limitations, notably into account the very limited observation field, due to the microscopical size of the diaphragm, the non-homogeneity of the vacuum at the level of the optical axis and the diffusion of the electrons which are retrodiffused by the object resulting in images of a poor grade.
The object of the present invention is to obviate these disadvantages by providing a scanning electron microscope assembly operating in situ, having a light and transportable structure, which may be directly laid on the object to be examined without any particular preparation of the latter while allowing a direct observation of the related object in the natural environment thereof, and enabling high magnification with an excellent depth of field (for instance, on the order of a thousand times greater than with an optical microscope) to be obtained for a quick, adaptable and non-destructive study in situ of, for example, aircraft wings, or for the checking of parts which are either machine-finished or worked with precision, such as glass lenses and mirrors for optical systems.
The scanning electron microscope assembly operating in situ, comprising a column unitary electron microscope, connection means to a system for controlling and checking the microscope and to a pumping system, comprises a supporting means for the column, connected to the lower part thereof, and an interior chamber having a lower open portion intended to be disposed tightly on a peripheral surface integral to the portion to be observed, means being provided for communicating the internal chamber with a transportable pumping system.
The support means comprises a peripheral skirt or wall withstanding pressure and defining the internal chamber and flexible sealing means limiting the lower open portion of the chamber, and intended to be applied on the bearing surface to be observed.
Other features and advantages of the present invention will appear from the following description of an embodiment, given by way of illustration but in any case not limiting, made in relation to the accompanying drawing in which:
The sole FIGURE is a diagramatic view of the scanning electron microscope assemb

REFERENCES:
patent: 3346736 (1967-10-01), Neuhaus
Patent Abstracts of Japan, Sep. 5, 1981, vol. 5, No. 141.

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