JPS62222555A - Record/read method for electron microscopic image - Google Patents

Abstract

PURPOSE:To enable always the regeneration of a high quality electron microscopic image of most excellent observableness by arranging the reading condition of the electron microscopic image corresponding to the sample to be observed. CONSTITUTION:The energy of an electron beam 2 carrying a magnified transmission image 8b of a sample 8 is stored on a storage fluorescent sheet 11 arranged in a portion maintained in a vacuum state. The sheet 11 is scanned two dimensionally by a deflected exciting light beam 12a incident on the sheet 11, then the sheet emits the accelerated fluorescence of an intensity corresponding to the energy level of the electron beam. This accelerated fluorescence is received with a photomultiplier 15 to read the light quantity optically. This reading output is amplified to an electrical signal S of proper level. Then it is transformed to a digital signal Sd by an A/D converter 24 in acquisition scale factor (latitude), and sent to an image regeneration device 26 after subjected to a signal processing such as frequency enhancement. Thereby the magnified transmission image 8b carried by the accelerated fluorescence can be regenerated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method for recording and reading electron microscope images, and in particular, it records electron microscopy images with high sensitivity, and also uses electric signals to enable various image processing. The present invention relates to a record reading method in which an electron microscope image is read at high speed.

(Technical Preface of the Invention and Prior Art) Electron microscopes have been conventionally known in which an electron beam transmitted through a sample is refracted by an electric or magnetic field to obtain an enlarged image of the sample. As is well known, in this electron microscope, an electron beam transmitted through the sample forms a diffraction pattern of the sample on the back focal plane of the objective lens, and the diffraction rays interfere again to form an enlarged image of the sample. It has become.

Therefore, if the enlarged image is projected by the projection lens, an enlarged image (scattered image) of the sample will be observed, and if the back focal plane is projected, the diffraction pattern of the enlarged sample will be observed. If an intermediate lens is placed between the objective lens and the projection lens, the focal length adjustment section of this intermediate lens will allow
A magnified image (scattering 1g+) or a diffraction pattern as described above is optionally obtained.

In order to observe the enlarged image or diffraction pattern (hereinafter collectively referred to as a transmission electron beam image) formed as described above, conventionally, a photographic film is generally placed on the imaging surface of a projection lens and the transmission electron beam is The image was exposed to light, or an image intensifier was installed to amplify and project the transmitted electron beam image. However, photographic film has the disadvantage that it has low sensitivity to electron beams and processing of clod images is troublesome.On the other hand, when using an image intensifier, the problem is that the sharpness of the image is low and the image is easily distorted. There is.

Furthermore, for the above-mentioned transmission electron beam images, gradation processing, frequency emphasis processing, density processing,
Image processing such as subtraction processing and addition processing, three-dimensional image reconstruction using Fourier analysis, image analysis for image binarization and particle size measurement, and diffraction pattern processing (crystal information analysis, (elucidation of lattice constants, dislocations, lattice defects, etc.), but conventionally in such cases, the microscopic image obtained by developing photographic film was read with a microphotometer and converted into electrical signals. The conventional method involves the complicated work of converting the electrical signal, for example, A/D converting the electrical signal, and then processing it with a computer.

In view of the above-mentioned circumstances, the present applicant has developed a technology that allows the electrical signals carrying the microscopic images to be directly obtained, so that electron microscopic images can be recorded and reproduced with high sensitivity and high image quality, and various processing can be easily performed. We proposed a new method for recording and reproducing electron microscope images (
Patent Application No. 1982-150175, Patent Application No. 59-21468
No. 0, etc.). This electron microscope image recording and reproducing method basically consists of:
2. Storage phosphor sheets, etc. that store electron beam energy
A dimensional sensor accumulates and records the electron beam that has passed through the sample in a vacuum state, and then the two-dimensional sensor is irradiated with light or heated to emit the accumulated energy as light, and this emitted light is detected photoelectrically. This image signal is used to reproduce the transmitted electron beam image of the sample.

In the above electron microscope image recording and reproducing method, since the electron microscope image is stored and recorded on a two-dimensional sensor such as a stimulable phosphor sheet, it is possible to record the electron microscope image with high sensitivity. The amount of electron beam exposure from an electron microscope can be reduced, and damage to the sample can be reduced.

In addition, with this method, it is extremely easy to perform image processing such as gradation processing and frequency emphasis processing on electron microscope images, and it is also extremely easy to perform image processing such as gradation processing and frequency emphasis processing on electron microscope images. Image analysis such as value conversion can also be performed much more easily and quickly than in the past by inputting the electrical signals into a computer.

However, when an electron microscope image is reproduced 1' by the above method, the quality of the reproduced electron microscope VT image may vary depending on the case.

(Objective of the Invention) Therefore, an object of the present invention is to provide an electron microscope image recording/reading method that eliminates the above-mentioned problems and enables reproduction of electron microscope images of the best image quality at all times.

(Structure of the Invention) The electron microscope image recording and reading method of the present invention was obtained based on the knowledge that the image quality of a reproduced electron microscope image is greatly influenced by the type of sample, and is based on the above-mentioned method. As described above, the electron beam transmitted through the sample is stored and recorded in a two-dimensional sensor in a vacuum state, and then the two-dimensional sensor is irradiated with light or heated to emit the accumulated energy as light, and this emitted light is used as a photoelectric sensor. In an electron microscope image recording/reading method in which an image signal is obtained by detecting the emitted light at It is characterized in that reading gain etc. are changed as appropriate.

The two-dimensional sensor described above temporarily accumulates at least a portion of the energy when exposed to an electron beam, and when external stimulation is applied later, at least a portion of the accumulated energy is transferred to light, electricity, or sound. It consists of a material that has the ability to emit in a detectable form. Specifically, as this two-dimensional sensor, for example, Japanese Patent Application Laid-Open No. 55-12429,
The stimulable phosphor sheets disclosed in Japanese Publications No. 55-116340, No. 55-163472, No. 56-11395, No. 56-104645, etc. are particularly preferably used. In other words, when a certain type of phosphor is irradiated with radiation such as an electron beam, part of the energy of this radiation is accumulated in the phosphor, and then when the phosphor is irradiated with excitation light such as visible light, The phosphor emits light (
(photostimulated luminescence). A phosphor that exhibits these properties is called a stimulable phosphor, and a stimulable phosphor sheet is a sheet-like recording medium made of the above-mentioned stimulable phosphor, and generally consists of a support and a stimulable phosphor. It consists of a stimulable phosphor layer laminated on a support. The stimulable phosphor layer is formed by dispersing the stimulable phosphor in a suitable binder, and if the stimulable phosphor layer is self-supporting, it will itself contain the stimulable phosphor. It becomes a light sheet and vines. Incidentally, an example of the stimulable phosphor for forming this stimulable phosphor sheet is disclosed in the above-mentioned Japanese Patent Application No. 59-2.
It is described in detail in the specification table of No. 14680.

In addition, as the above-mentioned two-dimensional sensor, for example,
47719, 55-47720, etc. can also be used. This thermal phosphor sheet is a sheet-like recording medium made of a phosphor (thermal phosphor) that emits accumulated radiation energy mainly through the action of heat as thermal fluorescence.

(Mr. Ms.) Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

FIG. 1 shows an electron microscope m obtained by an embodiment method of the present invention.
This figure shows an outline of a device for reading and writing 1II records. The mirror body 1a of the electron microscope 1 includes an electron gun 3 that emits an electron beam 2 at a uniform velocity, and at least one focusing lens 4 consisting of a magnetic lens, an electrostatic lens, etc. that focuses the electron beam 2 onto the sample surface. , a sample stage 5 , an objective lens 6 similar to the focusing lens 4 , and a projection lens 7 . The electron beam 2 transmitted through a sample 8 placed on the sample stage 5 is refracted by the objective lens 6 to form an enlarged transmitted image 8a of the sample 8. This enlarged transmitted image 8a is generated by the projection lens 7.
The image is projected onto the imaging plane 9 (8b in the figure).

Below the mirror body 1a is an electron microscope for carrying out the method of the present invention! A JI image recording/reading device 10 is arranged. This electron microscope image recording/reading device 10 includes a two-dimensional sensor (hereinafter referred to as a stimulable phosphor sheet 11) made of a stimulable phosphor fixed to the image forming surface 9 in a mirror body 1a, and an excitation Excitation means consisting of a light source 12 and a light scanning system 13, and a photomultiplier arranged to face the stimulable phosphor sheet 11 through a transparent window 14 provided on the peripheral wall of the mirror body 1a. (photomultiplier tube) 15 and an erasing light source 1G.

The stimulable phosphor sheet 11 is formed by layering the stimulable phosphor described above on a transparent support. Further, the excitation light source 12 includes, for example, a He-Ne laser, a semiconductor laser, etc., and the optical scanning system 13 includes first and second optical deflectors 13a and 13b, and a fixed mirror 13c.

As the first and second optical deflectors 13a and 13b, known optical deflectors such as a galvanometer mirror, a polygon mirror, a hologram scanner, and the like are used. The excitation light beam 12a emitted from the excitation light source 12 is deflected by the first optical deflector 13a, and is deflected by the second optical deflector 13a.
A direction perpendicular to the direction of the above-mentioned deflection (
It is deflected in the six directions of arrows in the figure) and is transmitted through a transparent window 21 in which lead glass or the like is fitted, for example, and enters the mirror body 1a.
The light is reflected by the fixed mirror 13c and is incident on the stimulable phosphor sheet 11. In this way, the stimulable phosphor sheet 11 is scanned in both the X and Y directions by the excitation light beam 12a. Although not shown, the excitation light beam 12a emitted from the excitation light source 12 is transmitted to the stimulable phosphor sheet 1.
After passing through a filter that cuts the wavelength region of the stimulated luminescence light (described in detail later) emitted by 1, and adjusting the rebeam diameter with a beam expander, the light deflector 13a113b
It is preferable that the beam be deflected by the stimulable phosphor sheet 11 and then passed through an fθ lens to form a uniform beam diameter.

The erasing light source 16 generates light within the excitation wavelength range of the stimulable phosphor sheet 11. A mirror 11 is disposed between the second optical deflector 13b and the fixed mirror 13c and can be placed in the optical path of the excitation light beam 12a or out of the optical path.

Erasing light 16a emitted by the erasing light source 16 is focused by a lens 18, and if the mirror 17 is set in a position where it enters the optical path of the excitation light beam 12a, it is reflected by the mirror 17 and the fixed mirror 13c, and is accumulated. The entire surface of the phosphor sheet 11 is irradiated. Further, a shutter 19 capable of blocking the electron beam 2 is provided in the mirror body 1a between the objective lens 7 and the stimulable phosphor sheet 11, and a shutter 19 that can block the electron beam 2 is provided between the stimulable phosphor sheet 11 and the photomultiplier 15. An optical shutter 22 is provided between them. A glass 20 equipped with an optical filter that transmits only the stimulated luminescence light emitted by the stimulable phosphor sheet 11 and removes the excitation light beam 12a is fitted into the light-transmitting window 14. In addition, the interior of the mirror body 1a, including the part where the stimulable phosphor sheet 11 is placed, is kept under vacuum by known means such as a vacuum pump during operation of the electron microscope, as in a normal electron microscope. will be maintained.

The output of the photomultiplier 15 is sent to the amplifier 23, A/
The signal is input to a D converter 24 and a signal processing circuit 25, and finally sent to an image reproduction device 26 such as a CRT. Note that a latitude control circuit 27, which will be described in detail later, is connected to the A/D converter 24.

Hereinafter, recording and reading of electron microscope images by the electron microscope image recording and reading apparatus 10 having the above configuration will be described in detail.

A sample 8 is placed on the sample stage 5, and an electron gun 3, a focusing lens 4,
When the objective lens 6 and the projection lens 7 are driven and the shutter 19 mentioned above is opened (the state shown in FIG.
The energy of the electron beam 2 carrying the enlarged transmitted image 8b is accumulated. During this electron beam exposure, the optical shutter 22 is preferably closed. Next, the shutter 19 is opened and the light shutter 22 is opened, and then, as described above, the excitation light beam 12a emitted from the excitation light source 12 and deflected in both the X and Y directions is made to be incident on the sheet 11. . The stimulable phosphor sheet 11 is two-dimensionally scanned by the excitation light beam 12a deflected in this manner, and the sheet 11 emits stimulated luminescence light whose intensity corresponds to the level of the electron beam energy.

This stimulated luminescent light is transmitted from the back side of the sheet 11 to a glass 2 equipped with an optical filter that removes the excitation light beam 12a.
The light is received by the photomultiplier 15 via the photomultiplier 15, and the amount of stimulated luminescence is read photoelectrically.

The output of the photomultiplier 15 carrying the light (1) of the above-mentioned bright 8 luminescent light is adjusted to an appropriate level "i" by the amplifier 23.
h signal (read image signal) S.

Next, this read image signal S is converted into a digital image signal Sd by the A/D converter 24 with a recording scale factor (latitude) set as described below, and then processed by the signal processing circuit 25, for example, by gradation processing, frequency The signal undergoes signal processing such as emphasis processing and is sent to the image reproduction device @26. By outputting an image based on the read image signal S in the image reproducing device 26 in this manner, the enlarged transmitted image 8b carried by the stimulated luminescent light is reproduced.

In addition to the above-mentioned CRT, an optical scanning recording device as shown in FIG. 2 can also be suitably used as the image reproducing device @26.

Hereinafter, a case in which an image is reproduced by the optical scanning recording apparatus shown in FIG. 2 will be briefly described.

The photosensitive film 100 is moved in the sub-scanning direction shown by the arrow Y in FIG.
01 is main-scanned in the direction of arrow X on the photosensitive film 100 by the optical deflector 104, and the laser beam 101 is modulated by the A10 transformer:IJ device 103 based on the image signal from the signal supply circuit 102. 100 to form a visible image.

If the signal output from the signal processing circuit 25 described above is used as the image signal for modulation, the stimulable phosphor sheets 1 to 1
The enlarged transmitted image 8b accumulated and recorded on the photosensitive film 100 is reproduced on the photosensitive film 100.

The image signal output from the signal processing circuit 25 may be immediately sent to the image reproducing device 26 for electron microscope image reproduction as described above, or it may be temporarily stored on a magnetic tape or magnetic tape for later image reproduction. Storage medium 2 such as a disk
8 may be stored.

Here, as a characteristic part of the method of the present invention, the recording scale factor (latitude) in the A/D converter 24
is appropriately changed by manually operating the latitude control circuit 27 depending on the type of sample 8. Specifically, for example, if the sample 8 is a biological sample, the latitude should be 2.0 or less, if it is a sample for diffraction pattern observation described below, the latitude should be 4.0 or less, and if it is another sample, the latitude should be 3.0 or less. is set to By setting the latitude in accordance with the sample 8 in this way, the contrast and resolution of the reproduced electron microscope image are set optimally in each case, and a reproduced image with excellent observability can be obtained. Note that the optimal latitude for each sample can be determined experimentally or empirically.

In order to obtain reproduced electron microscope images with excellent observability, it is most effective to set the above-mentioned recording scale factor according to the sample, so in this embodiment, only this recording scale factor is changed. However, the reading conditions for reading the stimulated luminescence light include the reading gain in the amplifier 23, etc., and the reading gain etc. may also be set according to the sample 8 if necessary. In addition to such reading conditions, conditions for signal processing (image processing) in the signal processing circuit 25 may also be set appropriately depending on the sample 8.

After reading the stimulated luminescence light, that is, reading the electron microscope image, as described above, the optical shutter 22 is closed, the mirror 17 is placed in the optical path of the excitation light beam 12a, Then, the erasing light source 16 is turned on. As a result, the surface of the sheet 11 is irradiated with the erasing light 16a emitted from the erasing light source 16. Even when the stimulable phosphor sheet 11 is irradiated with the excitation light beam 12a as described above, not all of the electron beam energy stored in the sheet 11 is released, and an afterimage may remain.

However, if the stimulable phosphor sheet 11 is irradiated with the erasing light 16a as described above, the afterimage is erased and the stimulable phosphor sheet 11 becomes reusable. Further, by this erasing light irradiation, noise components due to tIltJI elements such as 2H3Ra contained as impurities in the phosphor of the sheet 11 are also emitted. As the erasing light source 16, a tungsten lamp, a halogen lamp, an infrared lamp, a xenon flash lamp, a laser light source, or the like as shown in Japanese Patent Application Laid-Open No. 56-11392 may be used. Further, the excitation light source 12 for reading may also be used for erasing.

The case where the electron microscope image is reproduced as the final output image for observation of the sample 8 has been described above, but it is usually necessary to search the field of view and adjust the focus before recording and reproducing this final output image. This image for searching the visual field and adjusting the focus can be output to the image reproducing device 26 in exactly the same manner as described above, and the searching and focusing can be performed while observing this image. Note that it is convenient to use an OR'r@ display means as an image reproducing device that outputs images for this field of view search and focusing. A stimulable phosphor sheet is separately provided that can be moved between a position where it is irradiated and a position from which it exits, and an electron microscope image is read from the stimulable phosphor sheet at the exit position. A reading system may be provided and used for the above-mentioned field of view search and focusing.

Furthermore, the stimulable phosphor sheet for reproducing the final output image is also movable as described above, and in some cases, the chain part 1
Alternatively, the movable endless belt itself may be formed from a stimulable phosphor sheet, and the excitation light may be sub-scanned by the movement to read the image. However, if the image is read while the stimulable phosphor sheet 11 is fixed in the vacuum system as in the apparatus shown in FIG. 1, the apparatus can be simplified.
Its reliability can also be improved.

Next, a method for recording and reading the above-mentioned diffraction pattern will be explained. Figure 3 shows the diffraction pattern 8 of sample 8.
This shows how C is recorded. In this embodiment, the electron microscope 80 is equipped with an intermediate lens 81 between the objective lens 6 and the projection lens 7, and the diffraction pattern 8C of the sample 8 formed on the back focal plane of the objective lens 7 is used.
is enlarged and projected onto the imaging plane 9 by the intermediate lens 71 and the projection lens 7, which are focused on the back focal plane. In this case as well, if a stimulable phosphor sheet 11 is placed as a two-dimensional sensor on the image forming surface 9, an enlarged image of the diffraction pattern 8C by the transmitted electron beam 2 is stored and recorded on the sheet 11. This accumulated and recorded diffraction pattern 8C can be read in exactly the same manner as explained with reference to FIG. 1, and the read image can be displayed on a CRT or reproduced as a hard copy.

In addition, when a thermal phosphor sheet is used in place of the stimulable phosphor sheet 11 described above, in order to release the stored energy from this sheet by heating, a heating source that emits heat rays, such as a CO2 laser, is used. , it is sufficient to scan the thermal phosphor sheet with this hot wire.
1i (the description in Publication No. 5547720, etc.) may be referred to.

(Effects of the Invention) As explained in detail above, in the method for recording and reading electron microscope images of the present invention, since electron microscope images are stored and recorded on a two-dimensional sensor such as a stimulable phosphor sheet, It becomes possible to record images with high sensitivity, and therefore the amount of electron beam exposure of the electron microscope can be reduced, and damage to the sample can be reduced. Moreover, in the present invention, since the electron microscope image is read as an electric signal, it is extremely easy to perform image processing such as gradation processing and frequency emphasis processing on the electron microscope image, and it is also possible to perform image processing such as gradation processing and frequency emphasis processing on the electron microscope image. Image analysis, such as three-dimensional image reconstruction and image binarization, can also be performed much more efficiently and quickly than in the past, by inputting the above-mentioned electrical signals to a computer.

Roughly speaking, two-dimensional sensors that accumulate and record electron microscope images are
Since it can be reused by performing treatments such as light irradiation and heating, according to the present invention, electron microscope images can be reproduced more economically than when conventional silver halide photographic systems are employed.

In the present invention, since the reading conditions for electron microscope images are set according to the sample, it is possible to always reproduce a high-quality electron microscope with the best I-detectability.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for recording and reading electron microscope images by an embodiment method of the present invention, and FIG. 2 is a schematic diagram of an apparatus for reproducing electron microscope images based on read image signals obtained by the method of the present invention. FIG. 3 is a schematic diagram showing another example of an electron microscope to which the method of the present invention can be applied. 1.80...Electron microscope 2...Electron beam 8...Sample 9...Imaging plane of electron microscope 10...
Electron microscope image recording/reading device 11... adii phosphor sheet 12... excitation light source 12a... excitation light beam 13... optical scanning system T3a, 13b... optical deflector 15... frame First multiplier 16... Erasing light source 16a... Erasing light 23... Amplifier 24...
...A/D converter 25...signal processing circuit 26...
・Image reproduction device "a27...Latitude control circuit 1
Figure 2 (Volunteer procedure?-n) Author: Director General of the Patent Office June 1986
Relationship to the May 5 Incident Patent applicant Location 7th floor, Hauraiya Building, 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture (7318) Patent attorney Yanagi 1) Seishi (and 2 others) 5
, Date of amendment order None6, Number of inventions added by j1 due to amendment None7,
Subject of amendment Column 8 of [Detailed description of the invention] of the specification
6 Contents of amendment 1) Line 7 of line 17 of the specification

Claims (4)

[Claims] (1) A two-dimensional sensor that stores electron beam energy stores and records the electron beam that has passed through the sample in a vacuum state, and then the two-dimensional sensor is irradiated with light or heated to release the stored energy as light. , an electron microscope image recording and reading method for obtaining an image signal by photoelectrically detecting the emitted light, characterized in that reading conditions for detecting the emitted light are changed depending on the sample. Reading method. (2) The electron microscope image recording and reading method according to claim 1, wherein the detection of the emitted light is performed while the two-dimensional sensor is placed in a vacuum state. (3) A stimulable phosphor sheet is used as the two-dimensional sensor, the electron beam that has passed through the sample is stored and recorded on this stimulable phosphor sheet in a vacuum state, and then the stimulable phosphor sheet is exposed to excitation light. 3. A method for recording and reading an electron microscope image according to claim 1 or 2, characterized in that scanning is performed to emit fluorescent light, and the emitted fluorescent light is detected photoelectrically. (4) The electron microscope according to any one of claims 1 to 3, wherein the emitted light is detected while the two-dimensional sensor is fixed to the electron microscope image forming surface. Image record reading method.