JPH0160896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shutter device for an electron microscope, and particularly to a shutter device for performing microscopic diffraction in a scanning transmission electron microscope.

[Conventional technology]

When performing microscopic diffraction in a scanning transmission electron microscope, a hole is made in the fluorescent screen, and the magnified image that passes through the hole is placed in a transmission electron detector, which forms a diffraction image on a CRT in synchronization with rocking. The general function of an electron microscope is to place a film under a fluorescent screen, and normally observe it as is, and only when taking a photo, raise the fluorescent screen and shine an electron beam onto the film below to take a picture. For this reason, if the fluorescent screen has holes, it will be inconvenient for general use. Therefore, a shutter device that makes holes only when performing ultra-fine diffraction is required.

Figures 3 and 4 are perspective views showing conventional shutter devices, with Figure 3 being in normal use and Figure 4 being
The figure shows a case where ultra-fine diffraction is performed. In the figure, 1 is a large phosphor screen, and 2 is a small phosphor screen. A diaphragm hole 4 is formed in the small phosphor screen 2 on the optical axis 3, and the diaphragm hole 4 is connected to a shutter rotatable around an axis 5 on the back of the small phosphor screen 2. 6 is occupied. A hook 7 is provided at one end of the shutter 6 and projects to the front side through a groove 8 of the small fluorescent screen 2.

When the electron microscope is normally used, it is used in the state shown in FIG. When performing ultra-fine diffraction, as shown in Fig. 4, when the switch 9, which can be operated from outside the vacuum, is hooked to the hook 7 protruding from the shutter 6 through the small fluorescent screen 2 and pulled, the shutter 6 is 5, and the electron beam passes through an aperture hole 4 formed on the optical axis 3 and enters a transmission electron detector.

[Problem that the invention seeks to solve]

However, in such a conventional shutter device, since the switch 9 is not integrated with the small fluorescent screen 2, there is a risk of damaging the small fluorescent screen 2 during operation, and it is difficult to hook the switch 9 on the hook 7. In addition, since the small fluorescent screen 2 is equipped with a shaft 5, a hook 7, a groove 8, etc., there are problems such as shadows and the like that obstruct observation during general use.

This invention is intended to solve the above problems, and has a simple structure and operation that allows the shutter to be easily opened and closed, reliably blocks electron beams, secondary electrons, etc., and does not cause malfunctions or scratches. The object of the present invention is to provide a shutter device for an electron microscope that does not interfere with observation.

[Means for solving problems]

The present invention provides a fluorescent screen having an aperture, a holding plate having a hole at a position substantially corresponding to the aperture, holding the fluorescent screen and rotating it from an observation position through a diffraction position to a retracted position, and the aperture at the observation position. a shutter that rotates as the holding plate rotates so as to close the diaphragm and open the diaphragm at the diffraction position, and the diaphragm and the hole are arranged so as to be off the optical axis at the observation position and on the optical axis at the diffraction position. This is a shutter device for an electron microscope characterized by:

[Effect]

In the shutter device for an electron microscope of the present invention, at the observation position, the fluorescent screen is in a position where it is irradiated with an electron beam, and at this time, the aperture and the hole in the holding plate are off the optical axis, and the shutter is in a position where the aperture is closed. , the electron beam is blocked, the passage of secondary electrons is also blocked, and the festival is viewed on a fluorescent screen. When the holding plate is rotated from this position and the fluorescent screen is raised to the diffraction position, the shutter closes the diaphragm, and the diaphragm and hole are aligned on the optical axis, allowing the electron beam to pass through, resulting in microscopic diffraction. . When the holding plate is further rotated to move the fluorescent screen to the retracted position, the fluorescent screen and the like are removed from the beam spread angle of the electron beam, and photography or the like is performed.

〔Example〕

Hereinafter, the present invention will be described with reference to embodiments shown in the drawings. FIG. 1 is a sectional view showing an embodiment of the present invention;
FIG. 2 is an enlarged sectional view of a part thereof. In the figure, reference numeral 11 denotes a fluorescent screen, which has an aperture 12 and is attached to the upper side of a holding plate 13. Holding plate 13
has a hole 14 at a position approximately corresponding to the aperture 12,
It is fixed to a housing 17 via a holder 15 so as to be rotatable together with a shaft 16. The shaft 16 is rotated by a motor (not shown) to move the fluorescent screen 11 and the holding plate 13 to positions A, B, and C.

Position A is an observation position and is used when observing on the fluorescent screen 11 during normal use. Position B is a diffraction position where extremely small diffraction is performed, and the fluorescent screen 11 is slightly raised. The C position is a retracted position, and is used for photography, energy analyzer, scanning transmission electron microscope, etc. during general use.

A chamber 18 is provided on the lower side of the holding plate 13, and a hole 19 is formed in the lower part of the chamber 18. A shutter 21 is attached to an opening 20 in the side wall of the chamber 18 so as to rotate about a shaft 22, and a carbon 23 is provided at a portion facing the hole 14 at the A position. The center of gravity of the shutter 21 is set so that an arm 24 extends and constantly rotates in the direction of arrow X under its own weight, and is locked by a stopper 25. A stopper 26 is provided at the tip of the arm 24.
is formed and is adapted to be locked by the housing 17 and engaged with the engaging portion 27 of the holding plate 13 at the A position.

The aperture 12, the hole 14, and the hole 19 are located off the optical axis 3 and not on the same center line at the A position, and are arranged so as to be lined up on the optical axis 3 at the B position. 28 is an electron beam, and α indicates the beam aperture angle. In Figure 1, the A position is shown by a broken line, the B position is shown by a dashed line, the C position is shown by a solid line, and the second
In the figure, the A position is shown by a solid line, the B position is shown by a dashed line, and each part at the B position is indicated by the letter b.

In the above configuration, when the shaft 16 is rotated by driving a motor (not shown), the holding plate 13 is rotated, and the fluorescent screen 11 is accordingly rotated from the A position to the C position. In the shutter 21 at the A position, the stopper 26 is locked by the housing 17, and the shutter 21 is engaged with the engaging portion 27 of the holding plate 13. In this state, the shutter 21 closes the diaphragm 12 and the hole 14, and the carbon 23 faces the hole 14. Also, the aperture 12, hole 14 and hole 19 are connected to the optical axis 3.
Off the top and not in a straight line. Therefore, the electron beam 28 is blocked by the shutter 21 and does not pass downward, so that observation is performed on the fluorescent screen 11.

Considering only the electron beam 28 on the optical axis 3, the optical axis 3
If the diaphragm 12a is deviated from the diaphragm 12, the electron beam 28 will not pass below the fluorescent screen 11, but since the electron beam 28 will spread when observing an image on the fluorescent screen 11, a portion of the electron beam 28 will pass downward through the diaphragm 12. To prevent this, the holes 14 and 19 are provided so as not to be aligned on the same straight line, thereby blocking the electron beam 28.

In the A position, the shutter 21 hits the housing 17 and closes the aperture 12 and the hole 14, thereby blocking the electron beam 28 that has passed through the aperture 12 during image observation. The carbon 23 prevents the electron beams hitting the walls of the aperture 12 and the hole 14 from changing direction and passing through the hole 19, and also prevents the secondary electrons generated on the walls of the aperture 12 from passing through. Further, the scattered secondary electrons are confined in the chamber 18.

When the shaft 16 is rotated to rotate the fluorescent screen 11 to position B, the shutter 21b separates from the housing 17 and rotates in the direction of arrow X under its own weight, so that the carbon 23
b moves from the position opposite the hole 14b, and the shutter 2
1b opens to release the blocking of the aperture 12b and hole 14b, and the aperture 12b, hole 14b, and hole 19b are aligned on the optical axis 3, and the electron beam 28 on the optical axis 3 is transmitted through the aperture 12b, hole 14b, and hole 19b. 19
It passes downward through b and undergoes microscopic diffraction.

When the shaft 16 is further rotated and the fluorescent screen 11 is rotated to the C position, the fluorescent screen 11, the holding plate 13, and the parts attached thereto do not fall within the beam aperture angle α of the electron beam 28, so their shadows are not generated. figure,
Used for photography, energy analyzer, scanning transmission electron microscope, etc.

In the above-mentioned shutter device, the shutter 21 moves by its own weight in the rotation direction opposite to the rotation direction of the fluorescent screen 11, so the structure is simple and there are few failures. Furthermore, when the fluorescent screen 11 rotates, the diaphragm 12 and the holes 14, 19 are aligned in a straight line, making the operation easy, and there is no fear of failure, and there is no damage to the fluorescent screen 11 or obstruction to observation due to shadows or the like.

In the above embodiment, the shutter 21 is moved by rotation based on its own weight, but it may be moved in conjunction with a motor.

〔Effect of the invention〕

According to this invention, the fluorescent screen is rotated by the holding plate, the aperture is opened and closed by the shutter, and the aperture of the fluorescent screen and the holes of the holding plate are arranged so as to be aligned or deviated from the optical axis. The shutter can be easily opened and closed, it can reliably block electron beams, secondary electrons, etc., and there are no malfunctions or scratches, and it does not interfere with observation.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment, FIG. 2 is an enlarged sectional view of a portion thereof, and FIGS. 3 and 4 are perspective views of a conventional shutter device. In each figure, the same reference numerals indicate the same or corresponding parts, 3 is the optical axis, 11 is a fluorescent screen, 12 is an aperture, 13 is
is a holding plate, 14 and 19 are holes, 16 and 22 are shafts, 1
7 is a housing, 18 is a chamber, 21 is a shutter, 23 is carbon, and 28 is an electron beam.

Claims (1)

[Scope of Claims] 1. A fluorescent screen having an aperture, a holding plate having a hole at a position substantially corresponding to the aperture, holding the fluorescent screen and rotating it from an observation position through a diffraction position to a retracted position, and an observation position. a shutter that rotates with the rotation of the holding plate so as to close the aperture at the diffraction position and open the aperture at the diffraction position, the aperture and the hole being off the optical axis at the observation position and aligned on the optical axis at the diffraction position. A shutter device for an electron microscope, characterized in that it is arranged as follows. 2. The shutter device according to claim 1, wherein the shutter is rotatably mounted in a chamber having holes at positions corresponding to the holes in the holding plate. 3. Claim 1 or 2, wherein the shutter rotates under its own weight to open and close the diaphragm.
Shutter device as described in section.