JPS6132948A - Transmission-type electron microscope - Google Patents

Abstract

PURPOSE:To control the multiplying factor by controlling the electron lens current according to the current level obtained by interpolating the current level of an electron lens for a corresponding multiplying factor. CONSTITUTION:After the preselected multiplying factor is entered, a microprocessor 18 reads out one of the current levels of electron lenses 2-3 and 5- 9 stored in a memory element 19 and delivers the read current level to one of DA converters 11-17. A magnified image with the preselected multiplying factor can be observed on a fluorescent plate 10 by delivering the current level stored in the memory element 19 as it is to one of the DA converters 13-17. Therefore, it is possible to produce an arbitrary multiplying factor not a predetermined one by interpolating the current level stored in the memory element 19 by using an operator 20 and delivering the interpolation result to the DA converters 13-17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a transmission electron microscope, and particularly to improvement of magnification control.

[Background of the invention]

Conventionally, the magnification of a transmission electron microscope is determined by storing the current value of the imaging lens corresponding to each selectable magnification in advance in a memo IJK, and then changing the current stored in the memory by the magnification switching signal when the magnification is selected. Control was performed by reading out a value and outputting a current corresponding to this current value to an imaging lens (for example, Publication No. 49-22577).

However, such a magnification control method has the disadvantage that increasing the number of selectable magnifications requires an increase in memory capacity 2 and an increase in the size of the configuration. Furthermore, the number of selectable magnifications is limited by the number of current values stored in the memory, and there is a drawback that the operator cannot arbitrarily set the magnification.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission electron microscope that can set any magnification and can select and set many magnifications with a small memory.

[Summary of the invention]

The present invention calculates the current value of the electronic lens at an intermediate magnification between adjacent magnifications by performing interpolation calculation based on the current value of the electronic lens set corresponding to each predetermined type of magnification, By controlling the electron lens current using this current value, continuous magnification can be set.

[Embodiments of the invention]

FIG. 1 is a block diagram showing an embodiment of the present invention, in which an electron beam emitted from an electron gun 1 is converged by irradiation lens systems 2 to 3 and irradiates a sample 4.

The electron beam transmitted through the sample 4 is magnified by the imaging lens systems 5 to 9 to form an enlarged image of the sample on the fluorescent screen 10.

The current of each electron lens 2 to 3, 5 to 9 is passed through a DA converter 11
-17 by microprocessor 18. When the magnification is selected, the microprocessor 18 selects each of the electronic lenses 2 to 3 and 5 stored in the storage element 19.
The current values of ~9 are read out and output to each DA converter 11~F. At this time, if the current value stored in the memory element 19 is output as is to the DA converters 13 to 17, an enlarged image at a magnification selected and set in advance can be observed on the fluorescent screen 10. Therefore, if an interpolation calculation is performed using the calculation element 20 based on the current value stored in the storage element 19, and the result is output to the DA converters 13 to 17, it is possible to use an arbitrary magnification instead of a pre-selected magnification. It becomes possible to set the magnification of

Next, this interpolation calculation will be explained using FIGS. 2(a) and 2(b).

FIG. 2 shows the current values of the imaging lens systems 5 to 9 for a preset magnification. The current values corresponding to the black circle points in the figure are stored in advance in the storage element 19. .

Here, we will focus on magnification A and magnification B. Figure 2 (b
) is an enlarged view of the area between the magnifications A and B, and the current of each imaging lens 5 to 9 is shown as al-a5,
For magnification B, the value bl-b5 is stored. If a new magnification C is to be temporarily set between the magnifications A and H, the current value of each of the imaging lenses 5 to 9 can be obtained by performing the following interpolation calculation.

However, CI=current value of the imaging lens i=type of the imaging lens (i=1 to 5). Accordingly, the imaging lenses 5 to 9 for the magnification C are
The current value is determined, and by passing this current value through the imaging lenses 5 to 9, an enlarged image with a magnification of C can be obtained.

Note that although the first equation is a simple linear interpolation equation, the control accuracy of the magnification can be further improved by using a complicated interpolation equation.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to set an arbitrary magnification, and thus it is possible to continuously change the magnification. Furthermore, since the current value of the electronic lens, which must be stored for each magnification, can be calculated by interpolation calculation processing, the number of magnifications to be set in advance can be reduced, and the storage capacity of the memory can be reduced.

That is, there is an effect that many magnifications can be selected and set with a small memory configuration.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG.
) and (b) are diagrams showing the relationship between the electron lens current value and the magnification for explaining the basic principle of the embodiment.

Claims (1)

[Claims] 1. A memory means storing electron lens current values corresponding to a plurality of selectable magnifications, and reading out an electron lens current value corresponding to the selected magnification from among the electron lens current values stored in the memory means. In a transmission electron microscope equipped with a control means for controlling an electron lens current,
Interpolate the electron lens current values at adjacent magnifications,
A transmission electron microscope comprising an interpolation calculation means for calculating an electron lens current at an arbitrary magnification between adjacent magnifications, and configured to control a current value of the electron lens based on the calculation result of the interpolation calculation means.