JP3914787B2 - electronic microscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission electron microscope.
[0002]
[Prior art]
Some recent transmission electron microscopes have a TV camera in addition to a fluorescent screen. In such an electron microscope, the TV camera is arranged at the rear stage of the fluorescent plate, and when the fluorescent plate is retracted from the electron beam optical axis, a transmission electron image of the sample is taken by the TV camera.
[0003]
As the fluorescent plate, a large fluorescent plate is used, and as the TV camera, a high-resolution TV camera with a small area of an imaging unit is used.
[0004]
Usually, in an electron microscope equipped with such a TV camera, when a transmission electron image is observed at a low to medium magnification, a fluorescent plate capable of observing a relatively wide field of view is arranged on the optical axis. On the other hand, when observing an image at a high magnification, the fluorescent screen is retracted from the optical axis, an image with a relatively narrow field of view projected near the center of the fluorescent screen is captured by a TV camera, and the high magnification is displayed on the CRT screen. An image is displayed.
[0005]
Note that the magnification of the magnified sample displayed on the CRT screen and the magnification of the magnified sample projected on the fluorescent screen are the same when the lens conditions of the magnification lens system of the electron microscope are the same, than the latter. About 20 times higher.
[0006]
In an electron microscope equipped with such a fluorescent screen and a TV camera, the field of view of the observation image is moved by any one of the following methods (1) and (2).
(1) Mechanical visual field moving method: A method in which the sample moving stage on which the sample holder is set is moved in the xy direction by a mechanical mechanism such as manual or motor drive.
(2) Electromagnetic field movement method: A method in which an image shift coil for deflecting an electron beam transmitted through a sample in the xy direction is incorporated in a magnifying lens system, and a current flowing through the image shift coil is changed.
[0007]
By such a method of (1) or (2), the visual field movement of the image on the fluorescent screen or the CRT can be realized.
[0008]
In general, when observing an image at a low to medium magnification using the above-described fluorescent plate, the visual field movement is performed mainly using the mechanical method (1) that can increase the movement amount of the visual field. On the other hand, when observing an image at a high magnification with the TV camera described above, the method {circle around (1)} in which mechanical backlash and play exist is not often used, and the method {circle around (2)} that allows fine adjustment of the amount of visual field movement. Is used mainly for visual field movement.
[0009]
By the way, when the center axis of the electron beam coincides with the axis of the magnifying lens system, when the lens condition of the magnifying lens system is changed in order to change the image magnification, the transmission electron image on the fluorescent screen or the CRT becomes the fluorescent screen. Alternatively, the image is enlarged / reduced around the center of the CRT. That is, the transmission electron image is enlarged / reduced without being deformed.
[0010]
In contrast, in the method (2) described above, since the electron beam is deflected by the image shift coil, the electron beam is displaced from the axis of the magnifying lens system. When the lens condition of the magnifying lens system is changed in a state where this deviation amount is large, that is, in a state where the electron beam is greatly inclined from the axis of the magnifying lens system, the transmission electron image on the CRT or the fluorescent screen is enlarged with deformation / Reduced. For example, the image flows in a direction on the fluorescent screen or CRT.
[0011]
Therefore, in the conventional electron microscope, a function of automatically resetting (zeroing) the current flowing through the image shift coil every time the lens condition of the magnifying lens system is changed is incorporated.
[0012]
[Problems to be solved by the invention]
However, the following problems occur in an electron microscope incorporating such a function.
[0013]
That is, during high-magnification image observation using a TV camera, when the field of view to be observed is found by changing the current flowing through the image shift coil, the image shift coil current is reset as soon as the image magnification is changed, and the field of view where the folding angle is found The target field of view) may be lost on the CRT. This is due to the fact that the area of the TV camera's imaging unit is quite small. ₁ Even when it is tilted only, the image of the field of view found at the turning point is displaced outside the imaging range of the TV camera by resetting the image shift coil current.
[0014]
As described above, conventionally, when the image magnification is changed, there is a problem that the target field of view is lost on the CRT.
[0015]
On the other hand, the light receiving surface of the fluorescent screen is considerably larger than the imaging surface of the TV camera. Therefore, when observing a low-medium magnification image using a fluorescent screen, the electron beam is ₁ Greater than θ ₂ Even when tilted, even if the image shift coil current is reset as soon as the image magnification is changed, the movement of the target field of view can be followed on the fluorescent screen. In this case, if the visual field is moved using the mechanical method (1) described above so that the target visual field returns to the center of the fluorescent plate again, thereafter, an image that is enlarged / reduced around the center of the fluorescent plate is observed. can do.
[0016]
The present invention has been made in view of the above points, and an object thereof is to provide an electron microscope capable of smoothly moving the field of view of an observation image.
[0017]
[Means for Solving the Problems]
An electron microscope of the present invention that achieves this object includes a focusing lens that focuses an electron beam from an electron gun onto the sample, and a magnifying lens system that forms an enlarged image of the sample based on the electron beam transmitted through the sample by electron beam irradiation. When, A first observing means for observing a magnified image of the sample formed by the magnifying lens system; and a magnified image of the sample formed by the magnifying lens system, which is observed by the first observing means. Second observation means for observing an image corresponding to a part of the first observation means, and the first observation means for observing an enlarged image of the sample with any one of the first observation means and the second observation means. And switching means for selecting one of the second observation means, In an electron microscope provided with deflection means for deflecting an electron beam transmitted through the sample, When the magnified image of the sample is observed by the first observing means and the electron beam is deflected by the deflecting means, the magnifying lens system is controlled so that the lens condition of the magnifying lens system changes. At the same time, when the deflection unit is controlled so that the amount of deflection of the electron beam by the deflection unit becomes zero, while the enlarged image of the sample is observed by the second observation unit, the electron beam is Control the magnifying lens system so that the lens condition of the magnifying lens system changes while keeping the deflected state A control means is provided.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a diagram showing an example of an electron microscope of the present invention. First, the apparatus configuration of FIG. 1 will be described.
[0020]
In FIG. 1, reference numeral 1 denotes a lens barrel, and the lens barrel 1 is supported by a gantry 2. Inside the lens barrel 1, in order from the top, an electron gun 3, a first focusing lens 4, a second focusing lens 5, an objective lens 6, an x-direction image shift coil (deflection means) 7, a y-direction image shift coil (deflection) (Means) 8, the intermediate lens 9, and the projection lens 10 are arranged.
[0021]
The electron gun 3 generates an electron beam, and the electron beam from the electron gun 3 is focused by two stages of focusing lenses 4 and 5 to irradiate the sample 11. Then, the electron beam transmitted through the sample 11 is enlarged and imaged by a magnifying lens system including the objective lens 6, the intermediate lens 9, and the projection lens 10.
[0022]
The sample 11 is held by a sample holder (not shown), and the sample holder is set on a sample stage 12 that can move in the x, y, and z directions.
[0023]
Reference numeral 13 denotes a fluorescent plate (first observation means). The large fluorescent plate 13 is disposed in the image observation chamber 14 and is located at the rear stage of the projection lens 10. The fluorescent plate 13 is configured to be disposed (closed) on the optical axis O as shown by a solid line in FIG. 1 and retracted (opened) from the optical axis O as shown by a dotted line in FIG.
[0024]
Reference numeral 15 denotes a high-resolution TV camera. The TV camera 15 is attached to the lower part of the film camera room 16 and is located at the rear stage of the fluorescent screen 13. The camera head 17 of the TV camera 15 is positioned on the optical axis O, and the imaging unit of the camera head 17 is configured such that a layer of phosphor or the like is provided on the surface of the CCD, for example.
[0025]
The output signal of the TV camera 15 is supplied to the display means 18, and the TV camera 15 and the display means 18 constitute the second observation means of the present invention.
[0026]
Further, 19 is an image shift coil power supply unit, 20 is a magnifying lens power supply unit, 21 is a sample stage driving device, and 22 is a fluorescent plate driving device. The image shift coil power supply unit 19 controls the amount of current flowing through the image shift coils 7 and 8, the magnifying lens power supply unit 20 controls the amount of current flowing through the lenses 6, 9, and 10, and the sample stage driving device 21 is configured as described above. The sample stage 12 is driven, and the fluorescent plate driving device 22 drives the fluorescent plate 13.
[0027]
The power supply units 19 and 20 and the driving devices 21 and 22 are connected to the control means 23, and the operation board 24 is also connected to the control means 23. The operation board 24 is provided with a stage movement controller 25, an x image shift coil current varying knob 26, a y image shift coil current varying knob 27, a reset switch 28, a magnification varying knob 29, and a fluorescent plate drive switch 30. Yes.
[0028]
In the apparatus of FIG. 1, the inside of the lens barrel, the image observation room, and the film camera room are evacuated to a high vacuum by an evacuation device (not shown).
[0029]
The configuration of the electron microscope of FIG. 1 has been described above, but the operation of this apparatus will be described below.
[0030]
First, when observing an image at a low magnification using the fluorescent screen 13, the operator turns on the fluorescent screen drive switch 30 on the operation board 24. When the fluorescent plate drive switch 30 is turned ON, the control means 23 sends a drive signal for closing the fluorescent plate 13 to the fluorescent plate drive device 22. Upon receipt of this closing drive signal, the fluorescent screen driving device 22 closes the fluorescent screen 13 as shown by the solid line in FIG.
[0031]
When the fluorescent plate 13 is closed in this way, the transmission electron image of the sample 11 enlarged and formed by the magnifying lens system is projected onto the fluorescent plate 13. The image magnification on the fluorescent screen 13 at this time is a low magnification M _L Suppose that
[0032]
Therefore, the operator operates the stage movement controller 25 on the operation board 24 so that the visual field to be observed is at the center of the fluorescent screen. Based on this operation, the control means 23 sends a stage drive signal to the sample stage drive device 21, and the sample stage drive device 21 moves the sample stage 12 in the xy direction based on the drive signal. The field of view is located at the center of the fluorescent screen.
[0033]
Thus, when the target visual field is located at the center of the fluorescent screen, the operator operates the magnification changing knob 29 on the operation board 24 so that the image magnification of the target visual field is increased. Based on this operation, the control means 23 sends a lens control signal to the magnifying lens power supply unit 20, and the magnifying lens power supply unit 20 controls the current flowing through the coil of the magnifying lens system based on the control signal. The image magnification above increases.
[0034]
When the image magnification on the fluorescent screen rises to a certain magnification M and the field of view is moved slightly in this magnification state, the operator moves the field of view using an image shift coil in order to smoothly move the field of view. Do. For example, when it is desired to move the visual field in the horizontal direction (x-axis direction), the operator operates the x image shift coil current varying knob 26 on the operation board 24.
[0035]
Based on this operation, the control means 23 sends an image shift control signal (x, y) to the image shift coil power source 19, and the image shift coil power source 19 sends the image shift coils 7, 8 to the image shift coil 7, 8 based on the control signal. Control the flowing current. As a result, the electron beam transmitted through the sample 11 is deflected in the xy direction by the image shift coils 7 and 8, and the field of view moves in the horizontal direction on the fluorescent plate 13.
[0036]
When the field of view is moved in the horizontal direction in this way, the control unit 23 performs correction control so that current flows through both the x-direction image shift coil 7 and the y-direction image shift coil 8. This is to prevent the field of view from moving in a direction other than the horizontal direction due to image rotation. With such correction control, in the apparatus of FIG. 1, when the x image shift coil current variable knob 26 is operated, the visual field moves on the fluorescent screen 13 in the horizontal direction.
[0037]
On the other hand, to move the visual field in the vertical direction (y-axis direction), the operator operates the y image shift coil current varying knob 27 on the operation board 24.
[0038]
Based on this operation, the control means 23 sends an image shift control signal (x, y) to the image shift coil power source 19, and the image shift coil power source 19 sends the image shift coils 7, 8 to the image shift coil 7, 8 based on the control signal. Control the flowing current. As a result, the electron beam transmitted through the sample 11 is deflected in the xy direction by the image shift coils 7 and 8, and the field of view moves in the vertical direction on the fluorescent plate 13.
[0039]
Note that when the visual field is moved in the vertical direction in this way, the control unit 23 performs correction control so that current flows through both the x-direction image shift coil 7 and the y-direction image shift coil 8. This is to prevent the field of view from moving in a direction other than the vertical direction due to image rotation. With such correction control, in the apparatus of FIG. 1, when the y image shift coil current varying knob 27 is operated, the visual field moves on the fluorescent screen 13 in the vertical direction.
[0040]
Thus, by using the image shift coil, the field of view of the image can be moved slightly even in a state where the image magnification on the fluorescent screen is relatively high.
[0041]
When the electron beam is deflected by the image shift coils 7 and 8 as described above, the center axis of the electron beam is deviated from the axis O of the magnifying lens system as described above. That is, the electron beam is inclined from the axis O of the magnifying lens system.
[0042]
When the magnification varying knob 29 is operated so that the image magnification is further increased in the state where the electron beam is inclined as described above, the control means 23 outputs a lens control signal for increasing the image magnification based on the operation. This is sent to the magnifying lens power supply unit 20.
[0043]
At the same time, since the control unit 23 is in a state where an image is observed on the fluorescent screen 13 and the electron beam is deflected by the image shift coil, the current flowing through the image shift coils 7 and 8 is determined. A reset signal for resetting is sent to the image shift coil power supply unit 19.
[0044]
Under the control of the control means 23, the magnifying lens power supply unit 20 controls the current flowing in the coil of the magnifying lens system so that the image magnification increases from M to M ′. On the other hand, the image shift coil power supply unit 19 resets the current flowing through the image shift coils 7 and 8.
[0045]
As a result, the image I projected on the fluorescent plate 13 immediately before the visual field is moved by the image shift coil is displayed on the fluorescent plate 13. _S Magnified image I of (magnification M) _S '(Magnification M') is projected.
[0046]
In this case, as described above, since the current flowing through the image shift coils 7 and 8 is reset, the axis of the electron beam coincides with the axis of the magnifying lens system. For this reason, the enlarged image I _S 'The image I _S Corresponds to an image enlarged around the center of the fluorescent screen, and is an enlarged image without deformation.
[0047]
In this case, the field of view moves on the fluorescent plate as the image shift coil current is reset. However, since the light receiving surface of the fluorescent plate 13 is quite large, the movement of the field of view can be followed on the fluorescent plate.
[0048]
In the control means 23, when the image is observed on the fluorescent screen 13 and the electron beam is deflected by the image shift coil, the magnification changing knob 29 is operated so that the image magnification is lowered. Even in this case, a reset signal for resetting the current flowing through the image shift coils 7 and 8 is sent to the image shift coil power supply unit 19.
[0049]
The case where image observation is performed using the fluorescent plate 13 has been described above.
[0050]
On the other hand, when observing an image at a high magnification using the TV camera 15, the operator turns off the fluorescent plate drive switch 30 on the operation board 24. When the fluorescent plate drive switch 30 is turned off, the control means 23 sends a drive signal for opening the fluorescent plate 13 to the fluorescent plate drive device 22. Upon receipt of the opening drive signal, the fluorescent screen driving device 22 opens the fluorescent screen 13 as indicated by the dotted line in FIG.
[0051]
When the fluorescent screen 13 is thus opened, an image that has been projected near the center of the fluorescent screen 13 until then is picked up by the camera head 17 of the TV camera 15. The image signal from the camera head 17 is sent to the display means 18, and the transmission electron image picked up by the camera head 17 is enlarged and displayed on the CRT of the display means 18. Note that the image magnification on the CRT at this time is a high magnification M _H Suppose that
[0052]
When moving the field of view in this high magnification state, the operator moves the field of view using an image shift coil in order to smoothly move the field of view. The operator operates the x image shift coil current varying knob 26 to move the visual field in the horizontal direction, and operates the y image shift coil current varying knob 27 to move the visual field in the vertical direction. .
[0053]
By such an operation, the electron beam transmitted through the sample 11 is deflected in the xy direction by the image shift coils 7 and 8, and the field of view moves in the horizontal or vertical direction on the CRT. Also in this case, the control means 23 moves the field of view horizontally on the CRT when the x image shift coil current varying knob 26 is operated, and the y image shift coil current varying knob 27 is operated. Correction control is performed so that the visual field moves in the vertical direction on the CRT.
[0054]
As described above, by using the image shift coil, the field of view of the image can be smoothly moved even in a state where the image magnification on the CRT is high.
[0055]
Now, when the electron beam is deflected by the image shift coils 7 and 8, the central axis of the electron beam is deviated from the axis O of the magnifying lens system, and the electron beam is inclined from the axis O of the magnifying lens system.
[0056]
However, when observing an image at a high magnification using such a TV camera, the field of view on the CRT moves greatly only by tilting the electron beam slightly from the axis O by Δθ. For this reason, when observing an image at a high magnification using a TV camera, only a slight tilt of the electron beam can be used to move the visual field using the image shift coil.
[0057]
When the magnification varying knob 29 is operated so that the image magnification is further increased in the state where the electron beam is inclined as described above, the control means 23 outputs a lens control signal for increasing the image magnification based on the operation. This is sent to the magnifying lens power supply unit 20.
[0058]
Further, since the control means 23 is in a state where an image is observed with the TV camera 18 even when the electron beam is deflected by the image shift coil, the image shift coils 7 and 8 are in the current state. A reset signal for resetting the current flowing through the image shift coil is not supplied to the image shift coil power supply unit 19.
[0059]
Under the control of the control means 23, the magnifying lens power supply unit 20 has an image magnification of the M _H To M _H Control the current flowing through the magnifying lens coil so that it rises to '. On the other hand, the image shift coil power supply unit 19 controls the current flowing through the image shift coils 7 and 8 so that the current flowing through the image shift coils 7 and 8 is maintained as it is.
[0060]
As a result, the image I so far is displayed on the CRT of the display means 18. _TV (Magnification M _H ) Enlarged image I _TV '(Magnification M _H ') Is displayed.
[0061]
Thus, during image observation by the TV camera, even if the image magnification is changed, the current flowing through the image shift coils 7 and 8 is not reset. For this reason, the axis of the electron beam remains inclined from the axis of the magnifying lens system. However, since the inclination angle is suppressed to a slight Δθ as described above, the image magnification is M. _H To M _H Even if it is changed to ' _TV Is magnified with little deformation.
[0062]
As described above, in the electron microscope of FIG. 1, even if the image magnification is changed, the target field of view is not lost on the CRT, and the field of view can be moved smoothly.
[0063]
In the control means 23, the magnification variable knob 29 is operated so that the image magnification decreases when the image is observed by the TV camera 15 and the electron beam is deflected by the image shift coil. Even in such a case, the reset signal for resetting the current flowing through the image shift coils 7 and 8 is not supplied to the image shift coil power supply unit 19.
[0064]
In the apparatus of FIG. 1, when the reset switch 28 is pressed, the current flowing through the image shift coils 7 and 8 is forcibly reset.
[0065]
FIG. 2 is a diagram showing an operation flow in the electron microscope of FIG. 1, and this flow summarizes the above-described operation description.
[0066]
Heretofore, an example of the present invention has been described. Next, another example of the present invention will be described.
[0067]
FIG. 3 is a view showing another example of the electron microscope of the present invention. In FIG. 3, the same constituent elements as those in FIG. 1 are denoted by the same reference numerals as those in FIG.
[0068]
In FIG. 3, reference numeral 31 denotes a control means, and the image shift coil power supply unit 19, the magnifying lens power supply unit 20, the sample stage driving device 21 and the fluorescent plate driving device 22 are connected to the control means 31. Further, an operation board 32 is connected to the control means 31. The operation board 32 includes the stage movement controller 25, the x image shift coil current variable knob 26, the y image shift coil current variable knob 27, and a reset switch. 28, in addition to the magnification changing knob 29 and the fluorescent plate drive switch 30, non-reset magnification setting means 33 is provided.
[0069]
The operation of the apparatus shown in FIG. 3 will be described below. As an explanation of the operation, a case where an image is observed from a medium magnification to a high magnification using only a TV camera will be described.
[0070]
In that case, the operator adjusts the non-reset magnification setting means 33 on the operation board 32 so that the non-reset magnification M relating to the reset of the image shift coils 7 and 8 is obtained. _r Set. Normally, non-reset magnification M _r High magnification M _r Is set and its non-reset magnification M _r Is stored in the control means 31.
[0071]
Further, the operator turns off the fluorescent plate drive switch 30. When the fluorescent plate drive switch 30 is turned OFF, the control means 31 sends a drive signal for opening the fluorescent plate 13 to the fluorescent plate drive device 22. Upon receiving this drive signal, the fluorescent screen driving device 22 opens the fluorescent screen 13 as shown in FIG.
[0072]
When the fluorescent plate 13 is thus opened, a transmission electron image of the sample 11 enlarged and formed by the magnifying lens system is picked up by the camera head 17 of the TV camera 15. The image signal from the camera head 17 is sent to the display means 18, and the transmission electron image picked up by the camera head 17 is enlarged and displayed on the CRT of the display means 18. Note that the image magnification on the CRT at this time is M at medium magnification. _M Suppose that
[0073]
Therefore, the operator operates the stage movement controller 25 on the operation board 24 so that the visual field to be observed is at the center of the CRT. Based on this operation, the control means 31 sends a stage drive signal to the sample stage drive device 21, and the sample stage drive device 21 moves the sample stage 12 in the xy direction based on the drive signal. The field of view is located in the center of the CRT.
[0074]
Thus, when the target visual field is located at the center of the CRT, the operator operates the magnification changing knob 29 on the operation board 24 so that the image magnification of the target visual field is increased. Based on this operation, the control means 31 sends a lens control signal to the magnifying lens power supply unit 20, and the magnifying lens power supply unit 20 controls the current flowing through the coil of the magnifying lens system based on the control signal. The image magnification at is increased.
[0075]
And high magnification M with image magnification on CRT _H When the field of view is moved slightly in this high magnification state, the operator moves the field of view using an image shift coil in order to smoothly move the field of view. For example, when it is desired to move the visual field in the horizontal direction (x-axis direction), the operator operates the x image shift coil current varying knob 26 on the operation board 24.
[0076]
Based on this operation, the control means 31 sends an image shift control signal (x, y) to the image shift coil power supply unit 19, and the image shift coil power supply unit 19 sends the image shift coils 7 and 8 to the image shift coil 7 and 8 based on the control signal. Control the flowing current. As a result, the electron beam transmitted through the sample 11 is deflected in the xy direction by the image shift coils 7 and 8, and the visual field moves in the horizontal direction on the CRT.
[0077]
When the field of view is moved in the horizontal direction in this way, the control unit 31 performs correction control so that current flows through both the x-direction image shift coil 7 and the y-direction image shift coil 8. This is to prevent the field of view from moving in a direction other than the horizontal direction due to image rotation. With such correction control, in the apparatus of FIG. 3, when the x image shift coil current varying knob 26 is operated, the visual field moves in the horizontal direction on the CRT.
[0078]
On the other hand, to move the visual field in the vertical direction (y-axis direction), the operator operates the y image shift coil current varying knob 27 on the operation board 24.
[0079]
Based on this operation, the control means 31 sends an image shift control signal (x, y) to the image shift coil power supply unit 19, and the image shift coil power supply unit 19 sends the image shift coils 7 and 8 to the image shift coil 7 and 8 based on the control signal. Control the flowing current. As a result, the electron beam transmitted through the sample 11 is deflected in the xy direction by the image shift coils 7 and 8, and the visual field moves in the vertical direction on the CRT.
[0080]
When the field of view is moved in the vertical direction in this way, the control unit 31 performs correction control so that current flows through both the x-direction image shift coil 7 and the y-direction image shift coil 8. This is to prevent the field of view from moving in a direction other than the vertical direction due to image rotation. With such correction control, in the apparatus of FIG. 3, when the y image shift coil current varying knob 27 is operated, the visual field moves in the vertical direction on the CRT.
[0081]
Thus, by using the image shift coil, the field of view of the image can be moved slightly even in a state where the image magnification on the CRT is high.
[0082]
When the electron beam is deflected by the image shift coils 7 and 8 as described above, the center axis of the electron beam is deviated from the axis O of the magnifying lens system as described above. That is, the electron beam is inclined from the axis O of the magnifying lens system.
[0083]
With the electron beam tilted in this way, the image magnification on the CRT is the current M _H To M ₀ When the magnification changing knob 29 is operated so as to change to, the control means 31 changes the image magnification to M based on the operation. ₀ Is sent to the magnifying lens power supply unit 20. The magnifying lens power supply unit 20 has an image magnification of M _H To M ₀ The current flowing through the coil of the magnifying lens system is controlled so that
[0084]
At the same time, the control means 31 is in a state where the electron beam is deflected by the image shift coil and the image magnification on the CRT is M. ₀ The change magnification M ₀ And non-reset magnification M _r And compare. And the control means 31 is M ₀ ≧ M _r Then, the reset signal for resetting the current flowing through the image shift coils 7 and 8 is not supplied to the image shift coil power supply unit 19. On the other hand, the control means 31 is M ₀ <M _r Then, a reset signal for resetting the current flowing through the image shift coils 7 and 8 is sent to the image shift coil power supply unit 19.
[0085]
For example, in the control means 31, M ₀ ≧ M _r If it is determined, the image shift coil power supply unit 19 controls the current flowing through the image shift coils 7 and 8 so that the current flowing through the image shift coils 7 and 8 is maintained as it is.
[0086]
As a result, the image I (magnification M) is displayed on the CRT of the display means 18. _H ) Enlarged or reduced image I ′ (magnification M) ₀ ) Is displayed.
[0087]
Thus, the change magnification M ₀ Non-reset magnification M with preset _r If it is above, the image magnification is M ₀ Even if it is changed to, the current flowing through the image shift coils 7 and 8 is not reset. Therefore, even if the image magnification is changed, the target field of view is not lost on the CRT, and the field of view can be moved smoothly.
[0088]
At this time, since the current flowing through the image shift coils 7 and 8 is not reset, the axis of the electron beam remains inclined from the axis of the magnifying lens system. However, since the inclination angle is suppressed to a slight Δθ as described above, the image magnification is M. _H To M ₀ The image I is enlarged / reduced to the image I ′ with almost no deformation.
[0089]
On the other hand, in the control means 31, M ₀ <M _r If it is determined, the image shift coil power supply unit 19 resets the current flowing in the image shift coils 7 and 8.
[0090]
As a result, on the CRT of the display means 18, the image I displayed on the CRT immediately before the visual field is moved by the image shift coil. ₁ (Magnification M _H ) Enlarged or reduced image I ₁ '(Magnification M ₀ ) Is displayed. Thus, the field of view on the CRT moves with the resetting of the image shift coil current. However, in such a case, the magnification is M _H M ₀ And the field of view that we were looking at until now is image I. ₁ 'Can be confirmed above.
[0091]
In the apparatus of FIG. 3, when the reset switch 28 is pressed, the current flowing through the image shift coils 7 and 8 is forcibly reset.
[0092]
Further, in the apparatus of FIG. 3, the non-reset magnification M is set by the non-reset magnification setting setting means 33. _r When is not set, the operation of the apparatus of FIG. 3 is the same as the operation of the apparatus of FIG. That is, when observing an image with a fluorescent screen, the current flowing through the image shift coil is reset when the magnification is changed. On the other hand, when observing an image with a TV camera, the current flowing through the image shift coil is not reset even when the magnification is changed. .
[0093]
FIG. 4 is a diagram showing an operation flow in the electron microscope of FIG. 3, and this flow summarizes the above-described operation description.
[0094]
As mentioned above, although an example of this invention was demonstrated using FIGS. 1-4, this invention is not limited to this example.
[0095]
For example, in the above example, instead of the fluorescent screen 13, a wide-field imaging TV camera having a larger area than the imaging unit of the TV camera 15 may be arranged. In this case, the TV camera for wide-field imaging is configured to be arranged on the optical axis O and to be retractable from the optical axis O.
[0096]
In the above example, the image shift coil is disposed in the objective lens. However, the image shift coil may be disposed in the projection lens.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of the present invention.
FIG. 2 is a diagram showing an operation flow of the apparatus of FIG.
FIG. 3 is a diagram showing another example of the present invention.
FIG. 4 is a diagram showing an operation flow of the apparatus of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lens barrel, 2 ... Mount, 3 ... Electron gun, 4 ... 1st focusing lens, 5 ... 2nd focusing lens, 6 ... Objective lens, 7 ... x direction image shift coil, 8 ... y direction image shift coil, 9 ... Intermediate lens, 10 ... Projection lens, 11 ... Sample, 12 ... Sample stage, 13 ... Fluorescent screen, 14 ... Image observation room, 15 ... High resolution TV camera, 16 ... Film camera room, 17 ... Camera head, 18 ... Display means , 19 ... Image shift coil power supply unit, 20 ... Magnifying lens power supply unit, 21 ... Sample stage drive device, 22 ... Fluorescent plate drive device, 23 ... Control means, 24 ... Operation board, 25 ... Stage movement controller, 26 ... x image shift Coil current variable knob 27... Y image shift coil current variable knob 28. Reset switch 29. Magnification variable knob 30. Pitch, 31 ... control unit, 32 ... operation board, 33 ... non-reset magnification setting means

Claims (4)

A focusing lens for focusing the electron beam from the electron gun on the sample, a magnifying lens system for forming an enlarged image of the sample based on the electron beam transmitted through the sample by electron beam irradiation, and a sample formed by the magnifying lens system . A first observation means for observing a magnified image and a magnified image of a sample formed by the magnifier lens system, wherein an image corresponding to a part of the magnified image observed by the first observation means is observed. One of the first observation means and the second observation means for observing a magnified image of the sample with one of the second observation means and the first observation means and the second observation means. In the electron microscope provided with a switching means for selecting and a deflection means for deflecting the electron beam transmitted through the sample, an enlarged image of the sample is observed by the first observation means, and the electron beam is deflected Deflected by means The magnifying lens system is controlled so that the lens condition of the magnifying lens system changes, and the deflection unit is controlled so that the amount of electron beam deflection by the deflection unit becomes zero, When the magnified image of the sample is observed by the two observing means, the magnifying lens system so that the lens condition of the magnifying lens system changes while the electron beam is deflected by the deflecting means. An electron microscope comprising a control means for controlling the operation . The first observing means is a fluorescent screen on which an enlarged image of the sample is projected, and the second observing means is a TV camera that captures an enlarged image of the sample, and an output of the sample based on the output of the TV camera. claim 1, wherein the electron microscope is characterized in that a display means for displaying an enlarged image. A focusing lens for focusing the electron beam from the electron gun on the sample, a magnifying lens system for forming an enlarged image of the sample based on the electron beam transmitted through the sample by electron beam irradiation, and a sample formed by the magnifying lens system. In an electron microscope comprising observation means for observing a magnified image and deflection means for deflecting an electron beam that has passed through the sample, the electron microscope comprises control means for controlling the deflection means and the magnification lens system. When the magnifying lens system is controlled so that the magnification of the sample on the observation unit is M ₀ when the electron beam is deflected by the deflection unit, the magnification M ₀ is smaller than a predetermined magnification M _r. If, while the electron beam deflection amount by the deflecting means for controlling the deflection means so as to zero, and the magnification M ₀ is greater than the predetermined ratio M _r, electron by the deflecting means Electron microscope and controls the deflection means such deflection is maintained. The control means images the deflecting means so that the visual field on the observation means moves in the horizontal direction based on the output of the horizontal visual field movement instruction means that instructs to move the visual field on the observation means in the horizontal direction. The deflection means is controlled so that the visual field on the observation means moves in the vertical direction based on the output of the vertical visual field movement instruction means for controlling the rotation correction and for moving the visual field on the observation means in the vertical direction. electron microscope according to any one of claims 1 to 3, characterized in that the image rotation correction control.

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