JPH058548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electron microscope, and particularly to a photographic device for an electron microscope.

[Prior Art] Photographs of images are frequently taken using electron microscopes, but depending on the sample, it may be necessary to take a relatively long time to photograph them.

[Problems to be solved by the invention] While photographing such a sample, the filament of the electron gun may break, or the properties of the sample may change, resulting in a significant change in the intensity of the electron beam projected onto the photographic film, etc. There are cases where

In such a case, conventionally, the failure of photography cannot be noticed unless the photographic film is developed, so that all the time for photography and development is wasted.

The present invention solves these conventional drawbacks, and when the intensity of the electron beam projected onto the photographic photoreceptor changes significantly due to various causes, it is immediately notified and the photographing can be stopped or restarted. It is an object of the present invention to provide a photographing device for an electron microscope that enables early measures to be taken.

[Means for Solving the Problems] In order to achieve such an object, the present invention includes a start circuit that instructs the start of taking an electron microscope image;
A photographing device for an electron microscope, comprising: a shutter drive mechanism that opens the shutter for a set exposure time by supplying a start signal from the start circuit; and a photographic photoreceptor disposed after the shutter. , a detection means for detecting the intensity of the electron beam projected onto the photographic photoreceptor during photography; and a signal from the detection means is compared with a reference value to determine whether or not the signal is outside an allowable range. a first comparison circuit that generates a signal representing the start signal; a second comparison circuit that generates a signal representing whether or not a predetermined period has passed since the generation of the start signal; a response circuit that generates a response signal when a signal indicating that it is outside the permissible range is output and a second comparison circuit outputs a signal indicating that it is within the period; and a response signal from the response circuit. and a means for notifying an operator that the photographing has failed based on the above, and the predetermined period is set to be equal to or less than the exposure time.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing one embodiment of the present invention. In the figure, 1 is a projection lens of an electron microscope, and 2 is a shutter. The shutter 2 can be moved in the direction of arrow A by a shutter drive mechanism 3. 4 is a deflection coil, and a deflection signal is sent to the deflection coil 4 from a deflection power supply 5. 6 is a large fluorescent screen, and 7 is a small fluorescent screen. The large fluorescent screen 6 is rotatably provided around an axis 8, and the small fluorescent screen 7 is also rotatable about an axis 9 relative to the large fluorescent screen 6. In order to amplify the electron beam current incident on the small fluorescent screen 7, an amplifier 10 is connected to the small fluorescent screen 7, and the output signal of the amplifier 10 is sent to the sample and hold circuit 11, and also directly to the first comparison circuit. It has been sent to 12. The output signal of the comparison circuit 12 is sent to an AND circuit 13. 14 is a photographic film, 15 is an exposure time signal generation circuit, and 16 is a photographic film.
is the start circuit. A signal from the start circuit 16 is sent to the exposure time signal generation circuit 15 as well as to the shutter drive mechanism 3 and the deflection power source 5. On the other hand, exposure time signal generation circuit 1
The output signal of 5 is also sent to the shutter drive circuit 3, the deflection power supply 5, and further to the second comparison circuit 17. A reference signal is sent to the second comparison circuit 17 from a reference signal source 18 . The output signal of the second comparison circuit 17 is sent to the AND circuit 13.
The output signal is sent to the shutter drive mechanism 3 and also to a lamp drive circuit 20 that controls the lighting of the lamp 19. Also, deflection power supply 3
The second signal is the first signal to control the comparison timing.
The first comparison circuit 12 performs the comparison operation only at the timing when a signal for deflecting the electron beam EB is generated from the deflection power supply 3.

In such a configuration, with the small fluorescent screen 7 flush with the large fluorescent screen 6, the large fluorescent screen 6 is placed at a position intersecting the optical axis C as shown by the dotted line in FIG. 1, and the shutter 2 is opened. Fluorescent screen 6 in condition
The field of view for photographing is set while observing the electron microscope image projected at 7, and the exposure time T is set in the exposure time signal generation circuit 15 in accordance with the sample. Therefore, after the shutter 2 is moved to a position intersecting the optical axis C under the control of the shutter drive mechanism 3, the large fluorescent screen 6 is rotated around the axis 8 to the position shown by the solid line in the figure. At this time, the small fluorescent screen 7 is simultaneously rotated around the axis 9 to the position shown by the solid line in FIG. Therefore, the start circuit 16 is operated to generate a start signal as shown in FIG. 2a from the start circuit 16. Since this start signal is sent to the shutter drive mechanism 3, the shutter drive circuit 3 operates to remove the shutter 2 from the optical axis C, and an electron microscope image formed by the electron beam EB is projected onto the photographic film 14. Also, since the start signal is sent to the deflection power source 5, the deflection power source 5 generates a deflection signal as shown in FIG. 2b. Therefore, the electron beam EB is deflected toward the small fluorescent screen 7 by a time width t every time a preset time τ elapses. On the other hand, when the start signal is sent to the sample and hold circuit 11, the sample and hold circuit 11 samples and holds the output signal of the small fluorescent screen 7 at the timing shown in FIG. 2C. As a result, the output signal of the sample and hold circuit 11 becomes as shown in FIG. 2d. On the other hand, since the start signal is sent to the exposure time signal generation circuit 15, the exposure time signal generation circuit 15 falls with a time width equal to (Tt)/τ added to the preset exposure time length T, as shown in FIG. 2e. Generate a signal. (Tt)/τ is added because no image is exposed on the film 14 during the period when the electron beam is deflected off the optical axis by the deflector 4, so the shutter 2 is open only during that period. This is to set a longer time.

Now, after photographing is started in this way, the intensity of the electron beam projected onto the photographic film 14 is
As shown in Figure f, the timing t is approximately constant, but the timing t
Assume that as a result of the filament breaking in step 1, the intensity of the electron beam becomes approximately 0 thereafter. As a result, at timing t2 shown in FIG. 2b, the signal from the sample and hold circuit 11 and the amplifier 10
Since the difference in the signals sent to the first comparator circuit 12 via the 12-bit signal exceeds a preset limit value, the output signal of the first comparator circuit 12 becomes different from the previous low-level signal as shown in FIG. 2g. It becomes a high level signal. On the other hand, the second comparison circuit 17 is supplied with the signal shown in FIG. 2e from the exposure time signal generation circuit 15, but the output signal from the reference signal generation source 18 is
The level is set in advance as shown by the dashed line u in Figure e. This level is set from the following points of view. That is, when the level of the output signal from the exposure time signal generation circuit 15 becomes lower than this level, there is only a small amount of exposure time left, so even if the intensity of the electron beam changes significantly, it will not be treated as an exposure failure. This level serves as a standard for such determination, and for example, a value of about 10% of the initial value of the signal shown in FIG. 2e is selected.
As a result, the output signal of the second comparison circuit 17 is
As shown in FIG. h, after time t3, the level changes from high level to low level. Therefore, time t2
is earlier than time t3, the first comparison circuit 1
From the moment the output signal of the AND circuit 13 becomes high level, the output signal of the AND circuit 13 also changes to high level as shown in FIG. 2i. Therefore, the lamp drive circuit 2
0 lights up the lamp 19 in response to the high level output of the AND circuit 13, informing that the photographing operation has failed due to some kind of trouble. At the same time, the high-level output of the AND circuit 13 is sent to the shutter drive circuit 3, so the shutter drive circuit 3 immediately moves the shutter 2 onto the optical axis C and stops projecting the electron beam EB onto the photographic film. .

Therefore, since the operator can know that the photographing has failed, the operator replaces the filament and performs photographing again without developing the film.

Note that if the time t2 is after the time t3,
Even if the output signal of the first comparison circuit 12 changes to high level, the output signal of the first comparison circuit 17 remains low level, so the output signal of the AND circuit 13 does not become high level, and the lamp 19 does not turn on or shutter 3 closes, shutter 2 remains unchanged.
is kept open until T+(Tt)/τ has elapsed, and the film is developed, assuming normal photography.

FIG. 3 is for showing the main part of still another embodiment of the present invention, and many electron microscopes are equipped with a fluorescent screen 21 for focusing that can be inserted into and removed from the optical axis C above the large fluorescent screen 6. ing. The fluorescent screen 21 for focusing adjustment also has an amplifier 22 for measuring electron beam current. By the way, in the above-mentioned embodiment, in order to amplify the electron beam current flowing into the small fluorescent screen 7, an amplifier 10 dedicated to the small fluorescent screen 7 is provided, but in this embodiment, an amplifier 10 for extracting the electron beam current from the small fluorescent screen is provided. A lead wire is connected to the input stage of the amplifier 22. In FIG. 3, 23 is an amplifier for amplifying the electron beam current flowing into the large fluorescent screen 6, 24 is an ammeter, 25 and 26 are changeover switches, and p is the first
This is a terminal connected to the sample and hold circuit 11 and the first comparison circuit 12 shown in the figure.

In such a configuration, when photographing is to be monitored based on the output signal of the small fluorescent screen as in the first embodiment, the switch 26 may be connected as shown by the solid line in FIG.

In addition, when trying to measure the electron beam current flowing into the focusing fluorescent screen 21, the switch 26
is switched as shown in the dotted line, and the switch 25 is switched as shown in the dotted line. At this time, the electron beam does not enter the small fluorescent screen 7 at all, but since the large fluorescent screen 6 is horizontal, the amount of electron beam current that enters the small fluorescent screen 7 on the back side of the large fluorescent screen 6 is limited to the focusing fluorescent screen 21. It can be ignored compared to the amount of electron radiation incident on the ion beam, and poses no practical problem.

According to such an embodiment, one amplifier, which requires a high input impedance, can be saved.

FIG. 4 is a diagram showing still another embodiment. In the embodiment described above, in order to monitor the intensity of the electron beam projected onto the film surface, the electron beam current is detected intermittently. However, in this case, even if the intensity of the electron beam changes beyond a limit value, there will be a time delay until the shutter closes. Therefore, in this embodiment, a prism 28 having an opening 27 for passing the electron beam within the field of view is inserted into the optical axis C, and the electron beam EB' passing outside the field of view is directed to the upper surface of the prism 28. The scintillator layer 29 formed on the prism 28 converts the light into light, and the light is sent to the photodetector 31 via the light guide 30 integrated with the prism 28.
I'm trying to guide you. And this photodetector 3
By configuring the sample hold circuit 11 and the first comparison circuit 12 in the first embodiment to introduce the output signal 1 into the first comparison circuit 12, the same effect as in the first embodiment can be achieved.

Furthermore, this embodiment has the additional effect of being able to constantly monitor the intensity of the electron beam projected onto the photographic film, so that it is possible to deal with abnormalities without loss of time.

Furthermore, in the above-described embodiments, the case where the intensity of the electron beam projected onto the photographic film decreases during photographing is explained, but the present invention can be applied similarly even when the intensity of the electron beam increases during photographing. Applicable.

Furthermore, in the above-described embodiments, failure in photographing is visually notified, but it may be configured to be notified by audio or the like.

[Effects of the Invention] As is clear from the above explanation, according to the apparatus based on the present invention, the intensity of the electron beam projected onto the photosensitive member may fall outside the allowable range during photography due to some kind of trouble. If the device becomes outside, it can be reliably reported to the operator. Therefore, since time-consuming and wasteful phenomenon processing is not performed for unsuccessful photographing, appropriate measures for photographing again can be taken without loss time.

On the other hand, even if the intensity of the electron beam deviates from the permissible range after the end of imaging or before the start of imaging, this will not be falsely reported to the operator as an imaging failure, so false alarms will not bother the operator. do not have.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a timing diagram for explaining the operation of the embodiment of FIG. 1, and FIG. 3 is a main part of another embodiment of the present invention. FIG. 4 is a diagram showing essential parts of still another embodiment of the present invention. 1: Projection lens, 2: Shutter, 3: Shutter drive mechanism, 4: Deflection coil, 5: Deflection power supply,
6: Large fluorescent screen, 7: Small fluorescent screen, 8, 9: Axis, 1
0: Amplifier, 11: Sample and hold circuit, 1
2, 17: Comparison circuit, 13: AND circuit, 14:
Photographic film, 15: Exposure time signal generation circuit, 1
6: Start circuit, 18: Reference signal source, 19: Lamp, 20: Lamp drive circuit.

Claims (1)

[Claims] 1. A start circuit that instructs the start of taking an electron microscope image, a shutter drive mechanism that opens the shutter for a set exposure time by supplying a start signal from the start circuit, and a photographic device disposed after the shutter. A photographing device for an electron microscope comprising a photographing photoreceptor, a detection means for detecting the intensity of an electron beam projected onto the photographing photoreceptor during photographing, and a signal from the detection means being compared with a reference value. a first comparator circuit that generates a signal indicating whether or not the signal is outside the allowable range, and a second comparator circuit that generates a signal that indicates whether or not the signal is within a predetermined period from generation of the start signal. a comparison circuit; and a response signal when the first comparison circuit outputs a signal indicating that the signal is outside the allowable range and the second comparison circuit outputs a signal indicating that the signal is within the period. and a means for notifying an operator that imaging has failed based on the response signal from the response circuit, and the predetermined period is set to be equal to or less than the exposure time. Photography equipment.