JPH0588501B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a focusing device and a focusing direction for a transmission electron microscope for observing images on a television.

[Background of the invention]

Conventionally, a device commonly called a wobbler has been used as a focusing device for general transmission electron microscopes.
>). This wobbler device is a device that changes the incident angle of the electron beam on the sample over time, and if the electron microscope is out of focus, the image of the sample magnified on the imaging plane will waver. It looks like that. Therefore, the observer observes the movement of the sample image on the fluorescent plate while operating the wobbler device, and adjusts the focus by changing the current in the objective lens of the transmission electron microscope so that the movement is no longer recognized. It is something. The method using this device is widely used as a simple focusing method, but
As the amount of deviation from focus decreases, the movement of the image appears to be blurred, so
There was a problem that focusing could not be done with sufficient precision.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and method that clearly shows changes in an image due to changes in the incident angle of an electron beam in a television electron microscope and allows accurate focusing.

[Summary of the invention]

In order to achieve the above object, the focusing device for a television electron microscope according to the present invention includes a sample for obtaining an electron beam image, a wobbler that alternately changes the incident angle of the electron beam incident on the sample, and the above-mentioned wobbler. an electron lens that forms an image of the electron beam that has passed through the sample;
A television electron microscope comprising a television camera for photographing the image, display means for displaying the photographed image on a television screen, and a synchronization signal generator connected to the wobbler and the television camera. In the focusing device, the synchronizing signal generator operates the wobbler during the blanking period of the vertical scanning waveform of the television camera using the generated signal, and operates the wobbler at an integer fraction of the frequency of the vertical signal of the television camera.
By operating the wobbler at a frequency of , it is possible to clearly show changes in the image due to changes in the incident angle of the electron beam.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a focusing device for a television electron microscope according to the present invention;
FIG. 2 is an explanatory diagram of the waveforms of the vertical scanning current and electron beam deflection coil current of the television camera. In FIG. 1, an electron beam 3 emitted from an electron gun 2 in an electron microscope body 1 is deflected by a deflection coil 4 of a wobbler device, and the incident angle of incidence on a sample 5 is changed with a period f. The electron beam 3 transmitted through the sample 5 forms an image on a fluorescent surface 10 provided on a glass plate 9 by an objective lens 6, an intermediate lens 7, and a projection lens 8. This image is formed by an optical lens system 11 on the image pickup tube face plate of a television camera (hereinafter referred to as TV camera) 12, converted into an electrical signal, and displayed on a television monitor 13. At this time, if the transmission electron microscope is in focus,
Even if the angle of incidence of the incident electron beam 3 on the sample is changed, the image on the fluorescent surface 10 does not move, but if it is not focused, the image oscillates at the above-mentioned period f. In the present invention, a camera controller 15 for a TV camera and a deflection coil current generator 16 of a wobbler device are controlled by a synchronizing signal generated from a synchronizing signal generator 14. That is, the synchronization signal generator 1
4 generates synchronizing signals of frequency f and frequency Nf which is an integer multiple thereof, and these periodic signals control the deflection coil current and the vertical scanning current of the TV camera, respectively. As a result, the angle of the incident electron beam changes to TV
This can be done during camera blanking time.

FIG. 2 is a diagram depicting the vertical scanning current waveform of the TV camera and the deflection coil current waveform for the wobbler device according to the present invention with respect to elapsed time. Second
As shown in the figure, in the focusing device of the present invention,
The current waveform of the deflection coil of the wobbler device is switched during the blanking time of the vertical scanning current waveform of the TV camera. Therefore, the image on the television monitor 13 does not show any blur caused by the flow of the image while changing the incident angle, and when the transmission electron microscope is out of focus, the image on the television monitor 1
Image 3 becomes a complete double image. The observer only needs to adjust the objective lens current controller 17 so that the double image becomes a single image. When the image on the television monitor 13 does not become double even when the wobbler device is operated, but appears as a single image, the transmission electron microscope is in a correct focus state, excluding minute terms due to lens aberration.

In this embodiment shown in FIG. 1, the microcomputer 18 has a microcurrent value Δi for objective lens current.
is already remembered. This is particularly useful when you want to superimpose phase contrast on a low-contrast sample such as a biological sample to increase the contrast. By subtracting the above Δi from the objective lens current i ₀ at the time of correct focus, the objective lens 6 can be excited and an image showing appropriate contrast can be obtained.

〔Effect of the invention〕

As described above, the focusing device for a television electron microscope according to the present invention includes a sample for obtaining an electron beam image, a wobbler that alternately changes the incident angle of the electron beam incident on the sample, and a wobbler that alternately changes the incident angle of the electron beam incident on the sample. an electron lens for forming an image of the electron beam; a television camera for photographing the image; display means for displaying the photographed image on a television screen; and a synchronization signal connected to the wobbler and the television camera. In the focusing device for a television electron microscope, the synchronizing signal generator operates the wobbler during the blanking period of the vertical scanning waveform of the television camera according to the generated signal, and By operating the wobbler at a frequency that is an integer fraction of the vertical signal frequency of the camera, the incident angle of the incident electron beam can be changed within the blanking time of the TV camera. Changes in the image caused by the change in angle of incidence can be clearly seen as a double image on the television monitor, and since there is no blurring caused by image flow while changing the incident angle, it is possible to easily perform high-precision focusing. It is.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a focusing device for a television electron microscope according to the present invention, and FIG. 2 is an explanatory diagram of waveforms of the vertical scanning current and electron beam deflection coil current of the television camera in the above embodiment. be. 3... Electron beam, 4... Deflection coil, 5... Sample, 6... Objective lens, 12... Television camera, 15... Television camera controller, 16
...Deflection coil current generator, 17...Synchronization signal generator.

Claims (1)

[Scope of Claims] 1. A sample for obtaining an electron beam image, a wobbler that alternately changes the incident angle of the electron beam incident on the sample, and an electron lens that forms an image of the electron beam that has passed through the sample. A television electron microscope comprising a television camera for photographing the image, display means for displaying the photographed image on a television screen, and a synchronization signal generator connected to the wobbler and the television camera. In the focusing device, the synchronizing signal generator operates the wobbler during the blanking period of the vertical scanning waveform of the television camera using the generated signal, and operates the wobbler at an integer fraction of the vertical signal frequency of the television camera. A focusing device for a television electron microscope, characterized in that the wobbler is operated at a frequency of . 2. a sample for obtaining an electron beam image; a means for alternately changing the incident angle of the electron beam incident on the sample;
In a focusing method for a television electron microscope that has an electron lens that forms an image of the electron beam that has passed through the sample, and a television camera that takes the image, the incident angle of the electron beam that enters the sample is determined as described above. A step of alternately displaying images with different incident angles in the same image while changing the vertical scanning waveform of the television camera during the blanking period, and a step of adjusting the objective lens while determining the state of the image. A method for focusing a television electron microscope, comprising: