JP4994125B2 - Sample transfer method for transmission electron microscope - Google Patents

Description

  The present invention relates to a sample moving method for a transmission electron microscope, and more particularly to a sample moving method for a transmission electron microscope in which the sample moving speed is changed in accordance with the obtained frequency distribution of the brightness of the sample.

  When an image transmitted through a sample is obtained with a transmission electron microscope, the sample needs to be thin so that an electron beam or a charged particle beam can pass through the sample. Here, the thickness of the sample is, for example, about 1 μm when the applied voltage is 1000 kV, and about 0.1 μm when the applied voltage is 200 kV. Here, since the thickness of the sample is too thin, the sample cannot be opened and stabilized. Therefore, a mesh sample holder having a grid shape is used.

  FIG. 4 is an image view of a holder having a mesh structure. In the figure, reference numeral 1 denotes a mesh, which constitutes a grid structure holder. Therefore, the sample image cannot be seen in the portion covered with the mesh 1. 2 is a sample that can be seen through the mesh 1. That is, when a transmission image is observed, the image can be observed by an electron beam transmitted through a sample in a portion where the mesh portion has a hole, and the electron beam is blocked at the mesh portion, and an image cannot be obtained.

  FIG. 5 is a diagram showing the appearance of the sample hidden by the grid of the holder. In the figure, 4 is a grid, and 3 is a sample arranged below the grid 4. The image of the sample 3 where the grid 4 is placed is not visible.

As a conventional apparatus of this type, the light reflected by the document surface is main-scanned at each light accumulation time T / m designated for each line and converted into an electric signal, and after the electric signal is amplified, There has been known an apparatus that converts digital image data by an A / D converter, performs predetermined image processing on the converted digital image data, and outputs the processed image (see, for example, Patent Document 1).
JP-A-11-331513 (paragraphs 0015 to 0028, FIGS. 1 and 2).

  When observing a transmission image of a sample on a grid-shaped mesh-structure holder, if the sample is moved by moving the sample while observing a high-magnification image while moving the sample, the image is displayed. Can no longer be observed. At this time, the sample is moved to the position of the next mesh. However, the higher the magnification of the sample movement, the slower the normal speed is. In order to avoid this, there has been a problem that an extra operation is required to increase the magnification after moving down to the next grid by reducing the magnification and moving to the next grid.

  SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and a method for moving a sample of a transmission electron microscope that can improve operability by smoothly moving to the next mesh position when reaching the grid portion. The purpose is to provide.

This invention provides a transmission electron microscope, in the case of moving the sample held by the sample holder, acquires the transmitted image when the specimen is held in a sample holder, acquired sample and transmitted through the sample holder grid Statistical processing is performed on the image, and the speed of sample movement is controlled based on the statistical processing .
Then, a brightness distribution of the transmission image acquired as the statistical processing, to slow down the speed of the sample movement when moving in the direction in which brightness distribution becomes bright, the brightness distribution becomes darker When moving in the direction , the sample moving speed is controlled so as to increase the sample moving speed .

According to this invention, by using a statistical method to the transmission image acquired, the electron beam by detecting that the approaching to the grid portion, when approaching the grid portion is to increase the movement speed of the sample Thus, the operability can be improved by passing the area where data is not obtained at high speed.
That is, obtaining the brightness distribution of the transmission image acquired, slowing the speed of the sample movement can be obtained an image data of the sample when moving in the direction in which brightness distribution becomes bright, the brightness When the distribution is moving in the direction of darkening, the sample is shielded by the grid and cannot be seen , so that the operability can be improved by increasing the speed of the sample movement.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram of a transmission electron microscope. In the figure, 11 is an electron gun that emits an electron beam e, 12 is an irradiation optical system that focuses the electron beam e, 13 is a sample, and 14 is a sample holder that is placed on the sample 13 and holds the sample 13. The grid. The sample 13 is placed on a sample stage (not shown). Reference numeral 15 denotes a sample moving unit that moves the sample 13 in a predetermined direction. For example, a goniometer is used as the sample moving unit 15, and specifically, the sample stage is moved.

  Reference numeral 16 denotes an imaging optical system that forms an electron beam through the sample 13. Reference numeral 17 denotes a camera disposed at a position where an image is formed by the imaging optical system 16. Reference numeral 18 denotes an image processing apparatus that takes in an image captured by the camera 17 and performs predetermined image processing. Although not shown, the image processing device 18 includes an amplifier that amplifies an image captured by the camera 17, an A / D converter that converts the output of the amplifier into digital image data, and the like.

  Here, the image processing apparatus 18 performs statistical processing of the acquired image as will be described later, and controls the movement of the sample 13. For example, a computer is used. Reference numeral 19 denotes a display for displaying a transmission image captured by the camera 17. The sample moving unit 15 receives the sample moving signal from the image processing device 18 and moves the sample 13. The operation of the present invention will be described using the apparatus configured as described above.

FIG. 2 is a flowchart showing an example of the operation of the present invention.
(S1): First, a histogram is created (S1).
With the grid 14 placed on the sample 13, a transmission image of the electron beam is taken by the camera 17 and sent to the image processing device 18. The image processing device 18 amplifies the input image and converts it to digital data by an A / D converter, and then creates a histogram with the number of pixels having the brightness on the vertical axis and the brightness on the horizontal axis. .
(S2): Analysis of Histogram FIG. 3 is a diagram showing transition of an image and a histogram of the image when the sample is moved. (A) is a state where the sample 13 is not shielded at all, (b) is a state where the sample 13 is partially shielded from the shielding object 20, and (c) is a state where the sample 13 is almost shielded by the shielding object 20. Is shown. In addition, the grid 14 shown in FIG.

  In the state (a), the brightness frequency distribution is taken. The method for creating the frequency distribution is as follows. f1 is a frequency distribution characteristic in the state of (a). The horizontal axis is brightness, and the vertical axis is the number of pixels. The transmission image of the sample 13 shown in (a) is calculated for the number of pixels for each brightness. If the number of pixels having the brightness is plotted while changing the brightness little by little, the characteristic f1 is obtained. Since it is not obstructed by the shield, the distribution appears in the frequency part with a certain brightness.

  Here, when the sample 13 is partially hidden by the shield 20 as shown in (b), when the brightness frequency distribution is taken in the same manner as in (a), the characteristic is as shown in f2. It will be something. It can be seen that there are many elements in the darkest part. Next, when almost all the sample 13 is hidden by the shield 20, when the brightness frequency distribution is taken in the same manner as in the case of (a), the characteristic is as shown in f3. It can be seen that the number of pixels in the darkest part is extremely increased, and the number of pixels in the bright direction is extremely small.

After creating such a histogram, the image processing device 18 determines whether the obtained image data is in the bright direction or the dark direction.
(S3): The stage moving speed is increased.

When the histogram distribution progresses in the dark direction, it means that the image is closer to the grid, so the image processing device 18 sends a control signal to the sample moving unit 15 to increase the moving speed of the sample stage. Then, the histogram is analyzed based on the result of accelerating the stage movement, and the stage moving speed is further increased according to the analysis result. By performing such a series of operations, it is detected that the electron beam has approached the grid part, and when it reaches the grid part, the moving speed of the sample is increased to speed up areas where data cannot be obtained. It is possible to improve the operability by allowing it to pass through.
(S4): The stage moving speed is returned to normal.

  In the analysis of the histogram in step S2, when the histogram distribution advances in the bright direction, the sample is moving away from the grid, so the image processing device 18 sends a control signal to the sample moving unit 15 to move the sample stage. Return speed to normal. This makes it possible to accurately capture an image of the sample 13 portion.

  In the above-described embodiment, the case where a histogram (frequency distribution) is used as a statistical method of the captured image is taken as an example. However, the present invention is not limited to this, and other statistical methods may be used. it can. For example, the brightness distribution can be expressed using the standard deviation. If the brightness distribution is large, it is determined that the sample part is approaching and the stage moving speed is set to normal. return. Conversely, when the brightness distribution is small, it is determined that the grid is approaching, and the stage moving speed is increased. As a result, it is possible to improve the operability by passing the area where data is not obtained at high speed.

  As described above in detail, according to the present invention, there is provided a sample moving method of a transmission electron microscope that can improve operability by smoothly moving to the next mesh position when reaching the grid portion. be able to.

It is a block diagram of a transmission electron microscope. It is a flowchart which shows an example of operation | movement of this invention. It is a figure which shows transition of the image at the time of a sample movement, and the histogram of an image. It is an image figure of the holder of a mesh structure. It is a figure which shows the appearance of the sample hidden by the grid of the holder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Electron gun 12 Irradiation optical system 13 Sample 14 Grid 15 Sample moving part 16 Imaging optical system 17 Camera 18 Image processing apparatus 19 Display

Claims (1)

In the transmission electron microscope, when moving the sample held in the sample holder,
Acquire the transmission image with the sample held in the sample holder,
Statistical processing is performed on the acquired sample and the transmission image of the sample holder grid.
A method of moving a sample in a transmission electron microscope configured to control the speed of sample movement based on the statistical processing ;
Obtain the distribution of brightness of the transmission image acquired as the statistical processing,
If the brightness distribution is moving in the direction of brightening, the sample movement speed is slowed down, and if the brightness distribution is moving in the direction of darkening, the sample moving speed is increased.
A method for moving a sample of a transmission electron microscope.

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