JPS62241245A - Electron microscope - Google Patents

Abstract

PURPOSE:To make it possible to continuously rotate an electron microscopic image covering a wide range almost without changing an image magnification factor by gang control of excitation intensity of three lenses. CONSTITUTION:J1, J2 and J3 represent the excitation intensity of the first, second and third intermediate lenses form 6 to 8. Thereby, an image rotary angle theta determined by these three intermediate lenses from 6 to 8 is expressed at 100kV as follows: theta=0.0322X(J1+J2+J3). Further, when an imaging pattern of an electron microscopic image changes between a real image and a virtual image, the image rotation by 180 deg. is produced. Thereby, by changing-over said expression and the imaging pattern between the real image and the virtural imsge, the image rotation covering a wide range can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron microscope that can continuously rotate an electron microscope image without changing the image magnification.

[Prior Art] Improvements have been made to electron microscopes in order to rotate an electron microscope image projected onto a projection screen such as a fluorescent screen without changing the image magnification.

[Problem to be Solved by the Invention 1] However, in conventional electron microscopes, it has not been possible to continuously rotate the image over an extremely wide angular range without changing the observation magnification.

An object of the present invention is to solve these conventional drawbacks and provide an electron microscope that can rotate an electron microscope image over an extremely wide angular range without changing the observation magnification.

[Means for Solving the Problems] Therefore, the present invention has an irradiation lens system for focusing the electron beam from the electron gun to form a large sword on the sample, and at least three stages of imaging lenses. In an apparatus having an imaging lens system and a screen for projecting an electron microscope image formed on the imaging lens system, the electron microscope image projected onto the screen is used as a reference. and means for controlling the excitation intensity of the three stages of imaging lenses in conjunction with each other based on a signal from the instruction means, The present invention is characterized in that the electron microscope image can be continuously rotated without changing the image magnification of the microscope image.

[Embodiment] FIG. 1 is a diagram showing an embodiment of the present invention, in which 1 is an electron gun, 2 and 3 are focusing lenses, and 4 is a sample. 5
is an objective lens, and 6, 7.8 are the first . Second. The third intermediate lens 9 is a projection lens and 10 is a fluorescent screen. 1
1.12.13.14 are excitation power sources for the lenses 5, 6, and 7.8, respectively.

Note that the excitation mW source for lenses 2 and 3.9 is omitted.

15.16, 17.18 are these excitation power supplies 11.1, respectively.
This is a DA converter connected to 2, 13, and 14. Although DA converters 15, 16, 17, and 18 are not shown, each I1
It is connected to the CPU 20 via the 0 port and the pass line 19. A storage device 21 is connected to the CPU 2O via a path line 19. Furthermore, an input device 22 for instructing the rotation angle of the electron microscope image projected onto the fluorescent screen 10 is connected to the CPU 20 via a pass line 19. In the figure, 22r represents the rotation angle indicator.

Now, e is the electric charge (coulomb) of the electron, and mO is the static quality of the electron! (K(+), B(z) is the magnetic flux density of the lens magnetic field at coordinate 2 in one direction of light (Tesla), U* is the relativistically corrected electron acceleration voltage (Kv), J is the excitation intensity of the lens (Amperes)・turn), the image rotation angle θ (degrees) by the magnetic field lens is given by the following formula.

θ-e mOJ' B(z)dz-〇, 0337
6J/(sword) - Therefore, when Jl, J2, and J3 are the excitation intensities of the first, second, and third intermediate lenses, the image rotation angle θ by these three intermediate lenses is expressed as follows at 100 Kv. It will be done.

θ−0,0322x (Jl +J2−+−J3)・
(1) Furthermore, when the imaging pattern of an electron microscope image changes between a real image and a virtual image, a 180° rotation of the image occurs.

In this embodiment, image rotation is performed over a wide range by using the above equation (1) and switching the imaging pattern between real and virtual images. Therefore, when each image rotation angle θ is specified in the storage device 21, the first . Second. The third intermediate lens 6.7.8 is connected to the curve 111.1+2.7 in FIG.
1. ．． An excitation designation signal necessary for excitation according to No. 3 is stored. That is, each θn (n
= 1. 2゜3,..., +-1,t, i+i
, + +2, . . . , n+), the addresses corresponding to the first, second, . Excitation designation data for the third intermediate lens 5, 6.7 1') 1 (on), I)
2 (on) and D3 (on) are stored. Among these, DI (on) is data for capturing the excitation current value corresponding to the on of the curve IL1 in FIG. 2 in the first intermediate lens 6 when each On is instructed. , and others have similar correspondence relationships.

Further, at the address corresponding to the θn of the storage device 21,
Excitation designation data for designating the excitation current of the objective lens 5 is also stored. This stored value is used to cause the objective lens 5 to take the excitation current value shown by the curve ILo for each value of θn, as shown in FIG.

In such a configuration, if the rotation angle indicator 22'r of the input device 22 is used to direct the electron microscope image to form an angle θ, 1 with respect to the reference direction, then the CPLJ20
is the storage device 2 based on the instruction signal from the input device 22.
Excitation designation data D1 (θj>, D2 (θj), D3 (θj) of the address corresponding to the specified angle θj of 1
Read out. This read data DI (θj)
, D2 (θj), and D3 (θj) are converted into analog signals by the DA converters 16; 1'7' and 1e, respectively, under the control of the CPU 20. Each DA converter 1e: 17
．． 18 output signals are amplified by the excitation power supplies 12, 13, and 14, respectively. Second. Third intermediate lens6.
Sent to 7°8. Therefore, each of these lenses has curves r+-1, rr2. θj of r+-3
An excitation current with a value of flows.

As a result, as shown in FIG. A final image l' is formed on the fluorescent screen. At this time, the image formed on the fluorescent screen 10 is inclined by an angle θj with respect to the reference direction.

Similarly, J is set to the rotation angle indicator 22r of the input device 22.
:If the electron microscope image is instructed to be at an angle mθ with respect to the reference direction, the CPU 20 stores the information in the storage device 210.
Excitation designation data r)1 (θk) stored at the address corresponding to the angle θk.

02 (θk) and D3 (θk), the first
, 2nd. Similarly to the previous case, the third intermediate lenses 6, 7 and 8 each have a curve IL1°112.113 in FIG.
An excitation If current having a value at θk flows.

As a result, as shown in FIG. 5(b), after the sample 4 forms a first image T1' before the first intermediate lens 6, this image is further transferred to the second intermediate lens 7 and the third intermediate lens. Image 12 between lenses
-, the image 12'' is further formed as a third image r3 in front of the projection lens 9, and finally a final image 1f''' is formed on the fluorescent screen 101. At this time, the image formed on the fluorescent screen 10 is tilted at an angle θ of 1C with respect to the reference direction.

In this way, when an angle on the lower side of the dotted line C in FIG. 2 is designated by the input device, an image at the designated rotation angle is displayed on the fluorescent screen by taking the imaging pattern shown in FIG. 5(a).
0, and if an angle higher than dotted line C in Fig. 2 is specified by the input device, the specified rotation angle can be projected by taking the imaging pattern shown in Fig. 5(b). can be projected onto the fluorescent screen 10. Furthermore, as is clear from FIG. 2, the image rotation angle based on both imaging patterns is continuous at the dotted line C, so it is approximately -6
The image rotation angle can be changed continuously from 06 to +200'.

In addition, 1st. Second. When the excitation current value of each third intermediate lens is changed, the image plane of the objective lens 5 and the object plane of the first intermediate lens are slightly shifted, but in order to correct this shift, memory is stored for each value of θ. The objective lens excitation current designation data is read out from the device 21, and the excitation current value of the objective lens 5 is changed as shown in FIG. 3 for each value of θ, so this deviation is automatically corrected. .

In the above embodiment, the first .theta. corresponding to each .theta.
Second. The excitation current designation data for the third intermediate lens was determined in advance and stored in the storage device, but only the excitation designation data for discrete values of θ was stored, and the values between the discrete values were After calculating it, it may be sent to each lens power supply as excitation designation data.

Furthermore, a display means for displaying the image rotation angle may be connected to the CPU 20 to constantly display the angle of the electron microscope image relative to the reference direction.

[Effects of the Invention] As is clear from the above description, according to the present invention, the excitation intensities of the three lenses are changed in conjunction with each other, so that a wide range can be achieved without changing the image magnification. The electron microscope image can be rotated continuously over the entire range.

[Brief explanation of drawings]

Fig. 1 is a diagram showing one embodiment of the present invention, and Fig. 2 shows the first, second, . Third
Fig. 3 is a diagram for illustrating the excitation current value of the intermediate lens, and Fig. 3 shows the objective for each rotation angle necessary to correct the focus shift that occurs when the excitation current of the intermediate lens is changed for image rotation. FIG. 4 is a diagram to show the lens excitation current value, FIG. 4 is a diagram to show the contents stored in the storage device 21, and FIG. 5 is a diagram to explain two types of imaging patterns of an electron microscope image accompanying image rotation. FIG.

Claims (1)

[Claims] An irradiation lens system for focusing an electron beam from an electron gun and making it incident on a sample, an imaging lens system having at least three stages of imaging lenses, and an electron microscope in which an image is formed by the imaging lens system. In an apparatus having a screen for projecting an image, means for indicating an angle θ formed by an electron microscope image projected on the screen with respect to a reference direction, and a signal from the indicating means; and means for controlling the excitation intensities of the three stages of imaging lenses in conjunction with each other based on the above, and the electron microscope image can be continuously rotated without changing the image magnification of the electron microscope image. Characteristic electron microscope.