JPH09179975A - Image signal processor and scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily set a binarization level. SOLUTION: When the binarization level is set, conversion characteristics of converters 12, 13, and 14 are changed under the control of a controller 11. The converters 12 and 13 have standard conversion characteristics, i.e., characteristics for converting input data into output signals having intensities in stages. The converter 14, on the other hand, has multistage standard conversion characteristics similar to those of the converters 12 and 13 for input data of less than a level S, but sets the output signal intensity to 0 for input data of larger than the level S. Consequently, a black-and-white gradation image is displayed on the screen of an image display device 15 for the input of less than the level S and the output signal of the converter 14 becomes 0 for the input data of larger than the level S, so an image is displayed on the basis of the output of the converters 12 and 13.

Description

Detailed Description of the Invention

[0001]

The present invention relates to binarizing an image signal,
The present invention relates to an image signal processing device and a scanning electron microscope which emphasize and display only a characteristic part in an image.

[0002]

2. Description of the Related Art For example, in a scanning electron microscope, a focused electron beam is two-dimensionally scanned on a sample, and secondary electrons obtained from the sample are detected as the sample is scanned.
The detected secondary electron signal is once stored in the image memory, and the image signal stored in the image memory is supplied to the cathode ray tube to observe the scanned image of the sample.

In such a scanning electron microscope, only the image of the characteristic portion in the image is raised and observed. In this case, the image signal is binarized, and the image signal of a specific level or higher including the signal intensity of the characteristic portion is selectively set to 1 level (white level), and the image signal of the specific level or lower is set to 0 level (black level). ) Is supplied to the cathode ray tube.

FIG. 1 shows an example of a configuration for selecting the above-mentioned specific level. In the figure, M is an image memory in which an image signal is stored for each pixel, and the data of each pixel of the image memory M is supplied to the converter T. The output of the converter T is supplied to the image display device D such as a cathode ray tube.
The converter T outputs the input data from the image memory M as signal intensity suitable for the image display device D.

The converter T is, for example, a well-known look-up table (LUT), and as shown by a dotted line in the conversion graph of FIG. An output signal is obtained.

When the image signal is binarized, the output is set to 0 for input data below the specific input level S, and the output is set to 1 for input data higher than that. And As a result, only the pixels having the intensity equal to or higher than the specific input level S are set to the white level and the image display device D
Will be displayed above. In determining the specific level S, a grayscale histogram of the image is created and the level S is set using this histogram.

[0007]

The setting of the binarization level S using the above-mentioned histogram can be easily performed when the signal level of the characteristic region to be observed is clearly different from the others. Only the region desired to be observed can be raised on the display device 3. However, when a histogram in which the gradation of the image changes continuously is obtained, it is difficult to accurately set the binarization level S only from the histogram. In that case, the binarization level is set while looking at the display screen.

The setting of the binarization level while viewing the image is
Although the original image and the binarized image are overlapped, the image area of the signal intensity portion equal to or higher than the set level of the binarized image has a constant brightness (for example, white level). It is not possible to set the level in comparison with, and it takes a long time and the skill is required to set the final binarization level.

The present invention has been made in view of the above points, and an object thereof is to realize an image signal processing apparatus and a scanning electron microscope which can easily set a binarization level.

[0010]

According to a first aspect of the present invention, there is provided an image signal processing device comprising a plurality of converters for converting the data of each pixel of an image signal into a predetermined image signal intensity according to the value of each data. The output from the plurality of converters is combined and supplied to the color image display device, and a specific input level range is set for at least one converter of the plurality of converters. In the case of input data, the output signal strength is constant, and the specific level range can be arbitrarily changed.

According to the first aspect of the present invention, in any one of the plurality of converters for converting the signal supplied to the color display device, the input data in a specific level range has a constant output signal strength, The areas of the input data in the specific level range and other areas are displayed in different colors.

In the image signal processing device according to the second aspect of the present invention, three types of converters are prepared, and the output signals of the converters are the red signal, the green signal and the blue signal of the color image display device, respectively. .

According to the second aspect of the invention, similarly to the first aspect of the invention, the area of the input data in the specific level range and the other area are displayed in different colors. In the image signal processing device according to the invention of claim 3, a single input level range of the converter is set to a single level, and when the input data is higher or lower than the set level, it is constant. It is characterized in that the output signal intensity is set to.

According to the third aspect of the invention, the area of the input data having a level above or below the set level and the other area are displayed in different colors. In the image signal processing device according to the invention of claim 4, the setting of the specific input level range of the converter is 2
It is characterized in that one level is set, and in the case of input data of a level between the two levels, the output signal strength is constant.

According to the fourth aspect of the present invention, the area of the input data of the level between the two set levels and the other area are displayed in different colors. The scanning electron microscope according to the invention of claim 5 detects a signal obtained from the sample by scanning the sample with an electron beam, and displays a scanning image of the sample based on the detection signal. A plurality of converters that convert the data of each pixel of the signal into a predetermined image signal strength according to the value of each data are provided, and the outputs from the plurality of converters are combined and supplied to the color image display device. Of at least one of the converters, a specific input level range is set, and in the case of input data in the specific level range, the output voltage is configured to have a constant output signal strength. Is characterized in that it can be changed arbitrarily.

According to a fifth aspect of the present invention, in any one of the plurality of converters for converting the signal supplied to the color display device, the input data in a specific level range has a constant output signal strength, The areas of the input data in the specific level range and other areas are displayed in different colors.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 shows an example of a scanning electron microscope embodying the present invention, and 1 is an electron gun.
The electron beam generated from the electron gun 1 and accelerated is focused by the condenser lens 2 and the objective lens 3 and irradiated onto the sample 4.

The electron beam with which the sample 4 is irradiated is two-dimensionally scanned by the deflection coil 5. A scanning signal is supplied from the scanning circuit 6 to the deflection coil 5. Secondary electrons generated from the sample 4 by irradiating the sample 4 with the electron beam are detected by the secondary electron detector 7.

The detection signal of the detector 7 is amplified by the amplifier 8 and then supplied to the AD converter 9. The signal converted into a digital signal by the AD converter 9 is supplied to the image memory 10. The image memory 10 stores the detection signal at an address corresponding to the scanning of the electron beam on the sample based on the reference signal from the scanning circuit 6.

The signal data stored in the image memory 10 is read out under the control of the control device 11 and supplied to the first converter 12, the second converter 13, and the third converter 14. . The converters 12, 13, and 14 are LUTs, respectively, and each converter is controlled by the controller 11.

The output signals of the converters 12, 13, 14 are supplied to the color image display device 15. The output signal of the converter 12 is a red signal and the output signal of the converter 13 is a blue signal. The output signal of the container 14 is a green signal.
When the conversion operation of each converter is uniform, since a signal of the same intensity is obtained from each converter, a monochrome image is displayed on the image display device 15. The operation of such a configuration will now be described.

When observing a normal scanning secondary electron image, a scanning signal for scanning a predetermined range of the sample is supplied from the scanning circuit 6 to the deflection coil 5, and the electron beam is projected on the sample 4 based on the scanning signal. The two-dimensional scanning of the predetermined area of
The secondary electrons generated from the sample 4 based on this scanning are 2
It is detected by the secondary electron detector 7.

The detection signal of the detector 7 is supplied to and stored in the image memory 10 via the amplifier 8 and the AD converter 9. The image memory 10 integrates detection signals based on a large number of scannings of a predetermined region of the electron beam to obtain the SN of the image signal.
I try to increase the ratio. The signal of each pixel stored in the image memory 10 is sequentially read by the control of the control device 11 and supplied to the converters 12, 13, and 14.

In the case of observing a normal secondary electron image, the conversion characteristics of the converters are made uniform, and as a result, signals of the same intensity are obtained from the converters. A black and white image is displayed on the top. Next, the binarization operation will be described.

Before observing the binarized image, the binarization level is set. In that case, the conversion characteristics of the converters 12, 13, 14 can be changed by the control of the controller 11. FIG. 4 is a diagram showing conversion characteristics of each converter.
4A shows the conversion characteristic of the converter 12, FIG. 4B shows the conversion characteristic of the converter 13, and FIG. 4C shows the conversion characteristic of the converter 14.

As shown in FIGS. 4 (a) and 4 (b), the converters 12 and 13 have standard conversion characteristics, that is, characteristics in which output signal strength is converted to input data in multiple stages. ing. On the other hand, the converter 14 uses the converter 1 for input data below the level S with the binarization level S as a boundary.
Similar to Nos. 2 and 13, the multi-stage standard conversion characteristic is used, but the output signal strength is set to 0 for input data of level S or higher.

As a result, for input data of level S or lower, the output signal intensities of the converters 12, 13, 14 are equal, so that an image is displayed on the screen of the image display device 15 in black and white shading. . On the other hand, for input data of level S or higher, the output signal of the converter 14 becomes 0, so the converter 1
An image is displayed based on the outputs of 2 and 13. for that reason,
The input data portion of level S or higher becomes an image based on the red signal and the blue signal, and the image is displayed in yellow on the screen of the display device 15.

The operator observes the image on the display device 15 and operates the control device 11 to arbitrarily change the binarization level S so that the image in the yellow portion becomes a region to be binarized. After finally setting the binarization level,
As shown in FIG. 2, the conversion characteristics of the respective converters 12, 13, 14 are such that, with the binarization level S as a boundary, input data below that level is 0 level and input data above that level is 1 level. It is said that Therefore, on the display screen, only the characteristic regions are clearly distinguished and displayed with high brightness.

In the above-described embodiment, the input data of the binarization level S or higher is set to 1 level. Conversely, the input data of the binarization level S or lower is set to 1 level, and the levels of S or higher are set to 0 level. Also good. Further, the levels 1 and 0 are merely examples, and the level can be any value between 0 and 1.

In the above-described embodiment, the binarization is performed above and below the specific binarization level S as a boundary, but any two levels of the input data strength can be used as the binarization level. Alternatively, the image of the signal intensity between the two levels may be emphasized and displayed.

FIG. 5 shows the conversion characteristics of the converter in that case, FIG. 5 (a) shows the conversion characteristics of the converter 14, and the other converters 12, 13 have the conversion characteristics shown in FIGS. 4 (a), (b). ) Is a conversion characteristic. As shown in FIG. 5A, the conversion characteristic of the converter 14 is such that two input levels S1 and S2 are set, input data between the levels S1 and S2 is output as 0 level, and the level is equal to or lower than the level S1. Input data of level S2 and above is
It is regarded as a standard multi-step conversion characteristic.

As a result, only the image area where the input level falls between S1 and S2 is displayed in yellow on the display screen, and the other areas are displayed in black and white shading. While looking at this screen, operate the control unit 11 to set the levels S1 and S2.
After finally setting and, the conversion characteristics of the converters 12, 13, 14 are set to the characteristics shown in FIG. As a result, only the area of the input level between the levels S1 and S2 is displayed with high brightness, and the other areas are displayed dark.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the scanning electron microscope has been described as an example, but the present invention can also be applied to the case where other images such as an optical microscope image are binarized. Further, while the conversion characteristic of one converter is changed when the binarization level is set, the conversion characteristics of other converters may be changed according to the binarization level. In that case, the color of the binarized area is changed. Furthermore, the number of converters is not limited to three.

[0034]

As described above, according to the first aspect of the invention, a plurality of converters for converting the data of each pixel of the image signal into a predetermined image signal intensity according to the value of each data are provided, and a plurality of converters are provided. When the output from the converter is combined and supplied to the color image display device, a specific input level range is set for at least one of the plurality of converters, and input data in the specific level range is set. Is configured so that the output signal strength is constant, and the specific level range can be arbitrarily changed. Therefore, the area of the input data in the specific level range and the other area are displayed in different colors, and it becomes possible to select the setting level in a short time without obtaining the skill when obtaining the binarized image. .

In the inventions of claims 2 to 5, the area of the input data in the specific level range and the other area are displayed in different colors,
It is possible to select the setting level when obtaining a binarized image in a short time without requiring skill.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration for conventional binarization.

FIG. 2 is a diagram showing conversion characteristics of a converter during binarized display.

FIG. 3 is a diagram showing an example of a configuration of a scanning electron microscope for carrying out the present invention.

FIG. 4 is a diagram showing conversion characteristics of each converter.

FIG. 5 is a diagram showing conversion characteristics of a converter according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron gun 2 Condenser lens 3 Objective lens 4 Sample 5 Deflection coil 6 Scanning circuit 7 Detector 8 Amplifier 9 AD converter 10 Image memory 11 Control device 12, 13, 14 Converter 15 Image display device

Claims (5)

[Claims] 1. A color image display device comprising a plurality of converters for converting the data of each pixel of an image signal into a predetermined image signal intensity according to the value of each data, and synthesizing outputs from the plurality of converters. And a specific input level range is set for at least one of the plurality of converters, and in the case of input data in the specific level range,
An image signal processing apparatus configured to have a constant output signal intensity and capable of arbitrarily changing the specific level range. 2. The image signal processing device according to claim 1, wherein three kinds of converters are prepared, and the output signals of the converters are a red signal, a green signal and a blue signal of the color image display device. 3. A specific input level range of the converter is set by setting a single level so that a constant output signal strength is obtained in the case of input data having a level above or below the set level. The image signal processing device according to claim 1, which is configured. 4. The setting of a specific input level range of the converter is configured so that two levels are set, and in the case of input data of a level between the two levels, a constant output signal strength is obtained. The image signal processing device according to claim 1. 5. A scanning electron microscope which scans an electron beam on a sample to detect a signal obtained from the sample, and displays a scanning image of the sample based on the detection signal. A plurality of converters for converting to a predetermined image signal strength according to the value of each data are provided, and the outputs from the plurality of converters are combined and supplied to the color image display device, and at least the plurality of converters are provided. A specific input level range is set for one converter, and in the case of input data in the specific level range, the converter is configured to have a constant output signal strength, and the specific level range can be arbitrarily changed. Scanning electron microscope configured as described above.