JP2000268761A - Transmission electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the exposure time for taking a picture of an image with an electron microscope without using a mechanism for measuring the brightness of an observed image on a fluorescent screen or the like. SOLUTION: A transmitted image of a sample 4 is taken by a TV camera 7 and displayed on a monitor 11. And a brightness contrast signal from a signal processing circuit 9 and an average brightness signal per frame from an output circuit are input to a microscope control circuit 16. When the transmitted image of a sample 4 is filmed, a film 13 is set in a region of an electron beam after transmitting the sample 4 in a film camera 12. The microscope control circuit 16 determines the proper exposure time based on the input brightness contrast signal and the average brightness signal per frame, and outputs the determined exposure time to a shutter driving circuit 14. Then, a shutter is controlled by the shutter control circuit 14 based on the input exposure time for the transmitted image of the sample 4 being recorded on the film in a proper density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a transmission electron microscope that obtains an observation image of a sample by projecting a transmission beam transmitted through the sample onto a fluorescent plate, and particularly records this observation image on a film. Belong to the technical field of transmission electron microscopes.

[0002]

2. Description of the Related Art Conventionally, in a transmission electron microscope, a sample is irradiated with an electron beam generated by an electron gun through a condenser lens and an objective lens, and the transmitted beam transmitted through the sample passes through an intermediate lens, an energy filter, and a projection lens. An observation image of the sample is obtained by projecting the image on a fluorescent screen for image observation. In this transmission electron microscope,
It is also practiced to take a photograph of an observation image projected on a fluorescent plate and record it on a film. By the way, when recording an observation image of a transmission electron microscope on a film, when determining the exposure time, conventionally, the brightness of the observation image is converted from the electron flow density using a fluorescent screen to obtain an appropriate exposure time. Is determined.

[0003]

However, if the appropriate exposure time is determined by using a fluorescent screen as described above, after adjusting the field of view and focus with an image pickup tube such as a TV camera, the observation image is converted to a film. Before recording, the process of inserting the fluorescent plate into the beam path and measuring the brightness of the observation image is performed, so it takes time during this process, and sample contamination, sample damage or drift is a problem due to the effects of the beam irradiation time. It may be.

In a next-generation transmission electron microscope without an image observation room, which is expected to be developed more and more in the future, a fluorescent plate is not provided, but a mechanism such as a fluorescent plate is used only for determining the exposure time. Must be provided.
Further, the electron current measurement on the fluorescent screen is based on the reflection of the electron beam,
There is a case where an error occurs in the exposure time due to the influence of secondary electron emission and transmission.

The present invention has been made in view of such circumstances, and has as its object to photograph an observation image of an electron microscope without using a mechanism for measuring the luminance of an observation image such as a fluorescent screen. To provide a transmission electron microscope that can determine the exposure time for the transmission.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention of claim 1 is to observe an observation image of a sample by a transmitted beam of electrons transmitted through the sample with an image pickup tube,
In a transmission electron microscope configured to obtain a film image of the observation image by film-taking an observation image of the sample with a film camera, a shutter that performs the film shooting, a shutter driving circuit that drives the shutter, A luminance signal of the observation image obtained by the image pickup tube is input, and an exposure time is determined based on the luminance signal, and the control unit controls the shutter driving circuit based on the determined exposure time. It is characterized by having.

Further, according to a second aspect of the present invention, the luminance signal of the image pickup tube input to the control means includes a luminance contrast signal actually obtained by the image pickup tube and a luminance contrast signal per frame suitable for an operator's preference. An average luminance signal, and the control means determines the exposure time based on the luminance contrast signal and the average luminance signal.

[0008]

In the transmission electron microscope of the present invention having such a configuration, when an observation image of a sample is photographed on a film,
The control means determines an appropriate exposure time based on the luminance signal of the image pickup tube, and controls the shutter drive circuit based on the determined exposure time. As a result, the shutter drive circuit controls the operation so that the shutter has the determined exposure time. In this manner, a film image with an appropriate exposure for the observation image of the sample can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing an example of an embodiment of a transmission electron microscope according to the present invention. As shown in FIG. 1, in a transmission electron microscope 1 of this example, similarly to a conventional transmission electron microscope, electrons generated from an electron gun in a microscope column 2 are controlled by an irradiation system lens 4 and a sample 5 is transferred. The electron beam irradiated and transmitted through the sample 5 is imaged on a TV camera 7 controlled by an imaging lens 6 to obtain an observation image of the sample 5. Then, the TV camera 7 captures the observation image and outputs an image signal of the observation image. The image signal is output to the monitor 11 via the preamplifier 8, the signal processing circuit 9, and the output circuit 10, so that the monitor 11
Indicates an observation image of the sample 5.

On the other hand, a film camera 12 is provided above the TV camera 7 and below the microscope column 2. The film camera 12 causes the film 13 to advance into the region of the electron beam transmitted through the sample 5. It has become. The microscope column 2 includes a shutter drive circuit 14.
The shutter drive circuit 14 controls opening and closing of a shutter 15 disposed in a region of the electron beam transmitted through the sample 5.

The shutter drive circuit 14 includes the microscope control circuit 1
6 (corresponding to the control means of the present invention). The microscope control circuit 16
, A luminance contrast signal from the signal processing circuit 9 and an average luminance signal per frame from the output circuit 10 are input. The brightness contrast signal is T
The V-camera 7 is a signal indicating the actual luminance obtained from the observation image. The average luminance signal per frame is obtained by processing the luminance contrast signal of the TV camera 7 after the signal processing. Is a signal representing

In the transmission electron microscope 1 of this embodiment thus constructed, the transmission image of the sample 5 is T
Photographed by the V camera 7 and displayed on the monitor 11. At this time, the brightness contrast signal from the signal processing circuit 9 and the average brightness signal per frame from the output circuit 10 are input to the microscope control circuit 16, respectively. When a transmission image of the sample 5 is film-photographed, the film 13 is advanced by the film camera 12 into the region of the electron beam transmitted through the sample 5 and set. Then, the microscope control circuit 16 compares the input luminance contrast signal with 1
An appropriate exposure time is determined based on the average luminance signal per frame, and the determined exposure time is used as the shutter drive circuit 1
4 is output. Then, the shutter drive circuit 14 controls the shutter 15 based on the input exposure time, so that a transmission image of the sample 5 is recorded on the film surface with an appropriate degree of blackening.

As described above, the transmission electron microscope 1 of this embodiment
According to the method, since the exposure time is determined by the luminance contrast signal obtained from the TV camera image of the TV camera 7, the time from observation of the transmission image of the sample 5 to photographing can be shifted in a short time. Therefore, the effects of sample contamination, damage to the sample 5, drift, and the like can be reduced. Further, by using the luminance signal of the TV camera image, a mechanism for measuring the luminance of the observed image is not required in the transmission electron microscope having no image observation room. In addition, since the brightness of the observation image is not converted from the electron current density as in the related art and the brightness signal of the TV camera image is used, there is no error in measuring the electron current density.

Note that T inputted to the microscope control circuit 16
The luminance contrast signal of the V camera 7 is supplied to a signal processing circuit 9.
Instead of the actual luminance contrast signal composed of the processed output signal, an actual luminance contrast signal composed of the output signal amplified by the preamplifier 8 can be used as shown by a two-dot line in FIG. Also, the microscope control circuit 16
Determines the exposure time on the basis of the actual luminance contrast signal of the TV camera 7 and the luminance signal suitable for the operator's preference, but determines the exposure time based only on the actual luminance contrast signal of the TV camera 7. You can also decide.

[0015]

As is apparent from the above description, according to the transmission electron microscope of the present invention, when photographing a film,
Since the exposure time is determined based on the luminance signal obtained from the captured image of the imaging tube that has captured the observation image of the sample, it is possible to shift from observation of the transmission image of the sample to film shooting in a short time. Therefore, the irradiation time of the electron beam is shortened, and the influence of sample contamination, sample damage, drift, or the like can be reduced.

In addition, since the transmission electron microscope having no image observation room does not require a mechanism for measuring the luminance of the observation image, since the luminance signal of the image picked up by the image pickup tube is used. In addition, since the luminance of the observed image is not converted from the electron current density as in the related art, and the luminance signal of the image captured by the image pickup tube is used, errors in measuring the electron current density can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of an embodiment of a transmission electron microscope according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmission electron microscope, 2 ... Microscope column, 4 ... Irradiation lens, 5 ... Sample, 6 ... Imaging lens, 7 ... TV camera, 8 ... Preamplifier, 9 ... Signal processing circuit, 10 ... Output circuit, 11 ... Monitor, 12 ... Film camera, 13 ... Film, 14 ... Shutter drive circuit, 15 ... Shutter, 16
… Microscope control circuit

Claims (2)

[Claims] 1. An observation image of a sample by a transmission beam of electrons transmitted through the sample is observed by an image pickup tube, and an observation image of the sample is film-photographed by a film camera to obtain a film image of the observation image. A shutter for taking the film, a shutter drive circuit for driving the shutter, and a luminance signal of the observed image obtained by the image pickup tube, and exposing based on the luminance signal. A transmission electron microscope, comprising: at least control means for determining a time and controlling the shutter drive circuit based on the determined exposure time. 2. The luminance signal of the image pickup tube input to the control means is composed of a luminance contrast signal actually obtained by the image pickup tube and an average luminance signal per frame suited to an operator's preference, 2. The transmission electron microscope according to claim 1, wherein said control means determines the exposure time based on the luminance contrast signal and the average luminance signal.