JPS6342455Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an aperture device for an electron microscope, etc., which can prevent damage due to contact with a sample tube, lens magnetic pole, etc.

Several electron beam aperture devices are used in electron microscopes, particularly transmission electron microscopes, and among these devices, the objective lens aperture plays an extremely important role in terms of performance. The objective lens diaphragm is usually inserted between a narrow lens magnetic pole piece, so when inserting or moving the diaphragm device, or when moving the sample tube up and down or tilting the sample, the diaphragm and the sample tube must be Alternatively, the objective lens often comes into contact with the magnetic pole piece, thereby damaging the diaphragm and damaging the magnetic pole piece.

In order to prevent such contact accidents, conventionally, a device for moving the sample up and down or a device for tilting the sample is mechanically limited to prevent it from moving beyond a certain level. However, since such a device only regulates the moving side of the sample, and does not regulate the relationship with the diaphragm device, there is no way to prevent contact accidents due to changes in the relative position of the diaphragm device to the sample tube and objective lens. do not have.

In order to solve the above-mentioned drawbacks, a device was considered in which the aperture device was electrically suspended from the mirror body of the electron microscope, and a dangerous situation could be detected by the change in electrical resistance obtained when a sample tube etc. came into contact with the aperture. In the case of this device, since the diaphragm piece is used as a position detection means, the lead wire that carries the current must be housed in the shaft of the movable diaphragm, and hermetic seals are also required, resulting in a complicated structure. It is inevitable that it will be large, and it will be extremely difficult to ensure highly accurate movement as a diaphragm device.

The present invention was developed in view of these points, and although the aperture device is used as a position detection means, it eliminates the introduction of lead wires, has a simple structure, enables high-precision movement, and eliminates the possibility of contact accidents. Provided is a diaphragm device for an electron microscope, etc. that can prevent damage to the electron microscope.

The configuration of the present invention is an apparatus having an aperture mechanism including an aperture piece, a holder for holding the aperture piece, and a drive mechanism for moving the aperture piece, and at least a part of the drive mechanism is disposed outside the mirror body. The diaphragm mechanism is mounted to the mirror body in an electrically insulated manner, the outer periphery of at least a portion of the drive mechanism placed outside the mirror body is covered with an electrical insulator, and the diaphragm mechanism is electrically insulated from the mirror body. is connected through a resistor, the aperture mechanism is connected to a DC power source and held at a constant potential, and the voltage or current that changes when the aperture piece comes into contact with a member such as a sample tube or lens magnetic pole is detected. A diaphragm device for an electron microscope, etc. is characterized by a means for doing so.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In the figure, 1 is an objective lens, which is composed of an upper magnetic pole 2, a lower magnetic pole 3, a yoke 4, and an excitation coil 5. A sample chamber 6 is placed above the objective lens, and a sample stage 7 is disposed within this sample chamber. Although not shown, the sample stage is designed to be able to move freely within a plane perpendicular to the optical axis of the electron beam. This sample stage is provided with an upper and lower table 8, and a sample tube 9 having a sample is held in this table. A rack 10 is provided on the stand 8, and a pinion 11 is engaged with this rack. The pinion is connected to a rotary drive device 12 and rotated arbitrarily from the outside. The lower end of the sample cylinder is placed within the magnetic pole gap of the objective lens, and a movable diaphragm piece 13 is placed between the lower end and the lower magnetic pole 3. The aperture piece usually has a plurality of aperture holes of different diameters, and is adapted to be used by switching as appropriate. The aperture piece 13 is fixed to a holder 14 and inserted from outside the mirror body. The holder is held by a drive mechanism 16 having a knob 15,
It can be moved back and forth and left and right by operating the knob 15 and another knob (not shown) provided in a direction perpendicular to the page. The drive mechanism includes an electrical insulator 18
As a result, the diaphragm mechanism consisting of 13, 14, 15, and 16 is installed in an electrically floating state with respect to the mirror body of the electron microscope. A through hole 19 is provided in the electrical insulator 18, and a through hole 19 is provided in the electrical insulator 18.
A high-resistance element 20 of about 100 mL is inserted. The resistor 20
One end is electrically connected to the objective lens and the mirror body of the sample chamber, and the other end is electrically connected to the aperture drive mechanism, so that a minute current flows through this low antibody. The outer peripheries of the drive mechanism 16 and knob 15 are covered with electrical insulators 21 and 22, so that there is no risk of any danger even if the operator comes into contact with them. Reference numeral 23 denotes a DC power supply, which connects any part of the aperture mechanism, for example, the drive mechanism 16, via a resistor 24.
The aperture mechanism is floated at a constant potential (for example, 5V). 25 is an amplifier, and 26 is an abnormality detection circuit, which detects potential changes (or current changes) of the aperture mechanism. A signal from the detection circuit is sent to an indicator or alarm 27 to notify the operator of an abnormality. Further, the output of the detection circuit is also sent to the vertical movement drive mechanism 12 of the sample cylinder, and works to stop the drive immediately if an abnormality occurs. Of course, when the sample is tilted, the tilt driving device is connected to the detection circuit 26.
It will be stopped by a signal from.

In the above device, when there is no abnormality as shown in the figure, a slight current flows through the resistor 20, so that the electrons projected onto the aperture piece 13 do not charge up and reach the target. It is discharged to the mirror body through the resistor. On the other hand, for example, if the sample cylinder is lowered too much, the lower end of the sample cylinder
When the sample cylinder 9 and the aperture piece 13 come into contact with each other, the potential becomes the same, and current from the power source 23 flows through the aperture mechanism, the sample cylinder, the upper and lower stands, and the sample stage to the electron microscope mirror body at ground potential. The abnormality is detected by the circuit 26 as a change in potential, and is immediately alarmed by the alarm 27 and/or sent to the sample vertical movement drive device 12, so that the sample vertical movement is immediately stopped. It is preferable to provide a safety mechanism such that a similar alarm is issued and movement of the diaphragm mechanism is stopped even if the diaphragm piece comes into contact with the magnetic pole piece of the objective lens.

With the configuration described above, abnormal situations such as when the sample tube comes into contact with the diaphragm piece or when the diaphragm piece comes into contact with the magnetic pole piece of the objective lens can be immediately detected. Damage and damage to the magnetic pole piece of the lens can be prevented. Furthermore, since no lead wire for supplying current is passed through the movable shaft of the diaphragm mechanism, the structure is simple and compact, and there are no restrictions on the movement of the diaphragm device. Therefore, it is possible to realize a diaphragm device that can move with high precision. Furthermore, since the electrons incident on the aperture piece are discharged to the mirror body through a resistor, there is no risk of charge-up, and since the outer periphery of the aperture mechanism is covered with an electrical insulator, there is no danger to the operator. .

[Brief explanation of the drawing]

The accompanying drawings are partially sectional views showing one embodiment of the present invention. 1: Objective lens, 2: Upper magnetic pole, 3: Lower magnetic pole,
4: Yoke, 5: Excitation coil, 6: Sample chamber, 7:
Sample stage, 8: Upper and lower table, 9: Sample tube, 10:
rack, 11: pinion, 12: rotational drive device,
13: Squeezing piece, 14: Holder, 15: Pinch, 1
6: Drive mechanism, 18: Electrical insulator, 19: Through hole, 20: High resistance body, 21, 22: Electrical insulator,
23: DC power supply, 26: Abnormality detection circuit, 27: Display or alarm.

Claims (1)

[Claims for Utility Model Registration] 1. An aperture mechanism consisting of an aperture piece, a holder for holding the aperture piece, and a drive mechanism for moving the aperture piece, and at least a part of the drive mechanism is located outside the mirror body. In the apparatus, the diaphragm mechanism is mounted in an electrically insulated manner with respect to the mirror body, the outer periphery of at least a portion of the drive mechanism placed outside the mirror body is covered with an electrical insulator, and the diaphragm mechanism and the mirror body are The aperture mechanism is connected to the body through a resistor, and the aperture mechanism is connected to a DC power source and held at a constant potential, and the voltage changes when the aperture piece comes into contact with a member such as a sample tube or a lens magnetic pole. Or an aperture device for an electron microscope, etc., which is equipped with a means for detecting current. 2. The aperture device for an electron microscope, etc. according to claim 1, which has a means for displaying an abnormal signal from the detecting means or for issuing an alarm based on the signal. 3. A diaphragm device for an electron microscope or the like according to claim 1, which stops the movement of a sample vertical movement mechanism or a tilting mechanism in response to an abnormal signal from the detection means.