JPH10239027A - Film thickness measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quantitatively measure the film thickness of a slice by image processing. SOLUTION: This film thickness measuring device is provided with an image pickup means 2 photographing the slice of a sample, a slice position specification section 4 specifying the region where the slice is located in the image data outputted from the image pickup means 2 as a slice region, and a measurement section 6 calculating the thickness of the slice based on the color information of the slice region specified by the slice position specification section 4. The measurement section 6 is provided with a color distribution evaluating means reading the color information of the slice region specified by the slice position specification section 4 for each picture element and evaluating the color distribution in the region and a conversion processing means 10 specifying the standard color of the slice based on the color distribution evaluated by the color distribution evaluating means 8 and converting the color information of the specified color into thickness information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring apparatus, and more particularly, to a film thickness measuring apparatus for measuring the thickness of a sample using interference colors. A sample such as a biological specimen is, for example, a sample cut using an ultramicrotome,
In the present invention, in addition to the biological specimen, the film thickness of any substance exhibiting interference colors is measured.

[0002]

2. Description of the Related Art Heretofore, the measurement of the film thickness of a section of such a sample has been performed by an observer directly observing the interference color through an eyepiece of an optical microscope. Since the interference color of the thin film changes abruptly with a change in the thickness of the thin film, a thickness of several nm to several tens nm can be specified by the judgment of the color of the eye measurement.

[0003]

However, visual observation of interference colors with an optical microscope is inconvenient in that it is difficult to make uniform judgments and errors have been made by the inspector since most of the judgments are based on experience. Was.

That is, in the visual inspection, there is a disadvantage that the inspection result varies depending on the experience and physical condition of the inspector, and it is difficult to accurately determine the film thickness.

In addition, if a reference color sample is used for many years, color deterioration will occur due to fading, and the reference itself will change due to dirt. This also makes it difficult to accurately measure the film thickness. there were.

Further, in the measurement of the interference color by visual observation,
It is difficult to judge the change in thickness in one section according to the area, and therefore, in the conventional example, there is an inconvenience that the film thickness itself and the distribution of the film thickness in the section cannot be quantified. Was.

On the other hand, in today's technology, the number of cases where various visual inspections are automated by image processing is increasing. However, the measurement of the film thickness by the interference color is not known and needs to be newly developed. In this case, when the interference color in the slice is not uniform, the process of how to accurately specify the film thickness and the increase in the processing speed are specific development issues. Another problem is how to specify the position of the slice in the image.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the prior art and, in particular, to provide a film thickness measuring apparatus capable of quantitatively measuring the film thickness of a section by image processing. I do.

[0009]

Therefore, according to the present invention, there is provided an image pickup means for picking up an image of a section of a sample, and a section for specifying a region where the section is located in the image data outputted from the image pickup means as a section measurement area. The apparatus includes a position specifying unit, and a measuring unit that calculates the thickness of the section based on the color information of the section measurement area specified by the section position specifying unit.
Moreover, the measurement unit reads out color information of the intercept measurement area specified by the intercept position specifying unit for each pixel and evaluates the color distribution in the area, and the color distribution evaluation unit evaluates the color information. And a conversion processing unit for specifying the standard color of the slice from the distribution of the specified colors and converting color information of the specified color into thickness information. This aims to achieve the above-mentioned object.

The measurement section calculates the thickness of the section based on the color information of the section measurement area specified by the section position specifying section. At this time, the color distribution evaluation means reads out the color information of the intercept measurement area for each pixel and evaluates the color distribution in the area. For example, if the sections of the sample have the same thickness, the color distribution will be almost uniform, but if there is any malfunction during cutting such as an ultramicrotome, the film thickness will not be uniform, and in this case, The color distribution expands. For this reason, the color distribution evaluation means evaluates whether the film thickness is uniform. Further, the conversion processing means specifies a standard color of the section from the color distribution evaluated by the color distribution evaluation means, and converts the color information of the specific color into thickness information. Therefore, the standard thickness of the section is measured.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a film thickness measuring apparatus according to the present invention. The film thickness measuring device includes an imaging unit 2 for imaging a section of a sample, a section position specifying unit 4 for specifying a region where the section is located in the image data output from the imaging unit 2 as a section measurement region, A measurement unit 6 that calculates the thickness of the section based on the color information of the section measurement area specified by the position specifying unit 4.

Moreover, the measuring section 6 reads out color information of the intercept measurement area specified by the intercept position specifying section 4 for each pixel and evaluates the color distribution in the area. Conversion processing means 1 for specifying a standard color of the section from the color distribution evaluated by the color distribution evaluation means 8 and converting color information of the specific color into thickness information.
0.

The image pickup means 2 picks up an image of a thin film section cut by an ultramicrotome or the like. Depending on the configuration of the microtome, an image of the boat portion where the slices float may be taken.

The section position specifying section 4 specifies the position of the section in the image data picked up by the image pickup means 2. As the specific method, there are a method of automatically performing the processing by image processing and a method of displaying the image data on a CRT or the like and receiving an input of a position. Identify the area to be measured. In order to specify the section position by image processing, edge extraction processing and labeling are performed, and sequentially labeled areas are selected. In order to receive an input from the user, image data is displayed, and a coordinate input is received by a pointing device such as a mouse. In addition, the size of the region may be a part of the slice or the entire slice may be designated. When a part of the slice is used, the observation target region may be selected. Also, after hardening the specimen with resin etc.,
When cut together with the resin to form a section, the sample portion is used as a section measurement area.

The measuring section 6 is preferably provided with conversion data in which the relationship between the interference color and the film thickness is defined in advance. This data has various forms, such as the gradation handled by the imaging means,
It is created according to the required accuracy of the film thickness.

The color distribution evaluation means 8 evaluates the color distribution in the intercept measurement area. Specifically, using a statistical method, the difference in color that appears in each pixel in the intercept measurement area is evaluated numerically. For example, after calculating an average color, a method of calculating an error of each pixel based on the average color, or
The evaluation is performed by a method of calculating a standard deviation or a method of calculating a rate of change in color between adjacent pixels.

This evaluation has two uses: first, it helps to identify the standard colors in the slice, so that the effects of noise can be eliminated. Secondly, if the distribution is too wide, it means that the film thickness has changed extremely, so that it can be used to judge that use as an intercept is not possible.

The conversion processing means 10 converts color information into thickness information based on the color distribution in the intercept measurement area evaluated by the color distribution evaluation means 8. For example, RG
When the A / D conversion is performed at 256 gradations for each B, even a color change that is difficult to discern visually can be processed as digital data with high accuracy, so that the resolution generally increases compared to the visual observation. Further, quantitative film thickness measurement can be performed.

Next, by the evaluation of the color distribution evaluation means 8,
An example in which measurement of the film thickness is stopped will be described. In this case, when the color distribution evaluated by the color distribution evaluation means 8 varies beyond a predetermined threshold value, the conversion processing means 10 stops calculating the thickness of the intercept measurement area and externally outputs error information. An error processing function 12 for displaying is provided. As a result, the ultramicrotome may malfunction,
It is possible to automatically detect, by image processing, a section that is cut when the state of the sample is not good, is not uniform in film thickness, and is not suitable for subsequent observation. In addition, in conjunction with the main body of the ultramicrotome, it is possible to control to stop the cutting of the ultramicrotome.

Next, an embodiment in which the evaluation of the color distribution is performed based on an error will be described. As shown in FIG. 2, in this embodiment, the color distribution evaluation means 8 includes an average color calculation function 14 for calculating the average value of the color information in the intercept measurement area, and an average calculated by the average color calculation function 14. An error calculating function 16 for calculating an error for each pixel in the intercept measurement area based on the color.

The conversion processing means 10 uses the color information of the pixel with the smallest error calculated by the error calculation function 16 as the standard specific color of the intercept measurement area.
8 is provided. Thereafter, when the film thickness is measured based on the color information of the pixel specified by the discrimination specifying function 18, the influence of noise can be removed, and the film thickness of the section can be measured favorably.

In the example based on this error, the error processing function 1
2 performs error processing when the smallest error exceeds a predetermined threshold.

[0024]

FIG. 3 is an explanatory diagram showing the configuration of one embodiment of the present invention. In the embodiment shown in FIG. 3, the imaging means 2 includes a CCD camera 22 for imaging a film thickness measurement target, an A / D converter 24 for A / D converting the output of the CCD camera 22,
The digital data output from the A / D converter 24 is referred to as NT
And an NTSC converter 26 for converting the signal into an SC signal.

Further, an image storage section 28 for storing image data based on NTSC signals is provided downstream of the image pickup means 2 and upstream of the measurement section. The image storage unit 14 is configured by an internal or external storage device such as a floppy disk, a hard disk, and an MO disk. In the case of processing online, a RAM for video signals is used.

Further, in this embodiment, the section position specifying unit includes:
It is defined as a setting unit 5 that requests a user to input coordinates and specifies an intercept measurement area based on the input coordinates. Specifically, the setting unit 5 requests the input of coordinates that are the center of the measurement position and sets a measurement position based on the input coordinates, and a measurement position set by the measurement position setting function. A section measurement area specifying function for specifying a section measurement area for measuring film thickness and film thickness variation based on the position, a time interval setting function for setting a measurement time interval, and white for setting a color reference value It has a balance setting function. The white balance can be set by a camera control unit (CCU) integrated with the CCD camera.

In this embodiment, since the intercept measurement area has a simple shape such as a circle or a square, the processing speed is increased.
The section measurement area specifying function is a section measurement area with a circle having a radius of a predetermined number of pixels from the measurement position, and a rectangle surrounded by four sides of the predetermined number of pixels centered on the measurement position. I do.

Here, a display unit 30 for displaying various information and a film thickness output unit 32 for outputting the film thickness as a measurement result to the display unit 30 are provided in the measuring unit 6.

The measuring section 6 calculates an average value of the color data from the image data stored in the image storage section 14. If the image data is RGB color data, an average value is calculated for each of RGB.

The conversion processing means 10 of the measuring section 6 measures the color data of the image whose position is specified for the film thickness measurement object, and calculates the average value of the color data from the measurement result. Next, an error from the average value is calculated for each pixel (dot) in the measurement target area. Assuming that the average of RGB is Ra, Ga, and Ba, respectively, an error e for each pixel (dot) in the intercept measurement area
Is represented by the following equation (1).

E ² = (Ra-R) ² + (Ga-G) ² + (Ba-B) ² ... Equation (1)

The thickness A is determined based on the color of the pixel in which the error e is minimized with reference to the conversion table shown in FIG.

FIG. 5 is a block diagram showing the configuration of the hardware resources of this embodiment. The image storage unit 28, the measurement unit 6, the setting unit 5, the film thickness output unit 32, and the display unit 30 in FIG. 3 can be realized by a video capture board 34 and a personal computer 38. This is because, when a program that uses the personal computer 38 as an execution device of the measuring unit 6 or the like is installed in the personal computer, the personal computer becomes a logic circuit that operates as the measuring unit 6 or the like.

Such a program can be stored in a storage medium such as a CD-ROM or a floppy disk and distributed.

Next, the operation of this embodiment will be described with reference to FIG. First, a slice is imaged (step S1). Then, for example, image data 2a shown in FIG. 7 is obtained. At this time, if an inverter type illumination is used instead of a normal fluorescent lamp or incandescent lamp, interference colors can be satisfactorily photographed. In the example shown in FIG. 7, a plurality of samples S are floating on the boat 40 of the microtome. Next, the position of the slice for measuring the film thickness is input (step S2). Here, it is assumed that the sample S at the center of the boat is input as the intercept position. Then, the setting unit 5 specifies the intercept measurement region R.
Here, the section measurement area is circular. The setting for specifying the intercept measurement area is performed based on the designation of the radio button or the input cell by displaying the setting window 5a shown in FIG. The measurement area in FIG. 8 means a section measurement area.

Further, the measuring section 6 calculates the average color of the intercept measurement area (step S3). Further, based on the average color, the color error of each pixel in the intercept measurement area is calculated by the above equation (1) (step S4).

Here, it is determined whether or not the smallest error value among the errors of the respective pixels in the intercept measurement area is equal to or smaller than a predetermined threshold value (step S5). If the thickness exceeds a predetermined threshold, the film thickness is not uniform.
Error processing is performed (step S6). On the other hand, if it is equal to or smaller than the threshold value, the color information of the pixel having the smallest error is converted into the thickness information shown in FIG. 4 (step S7). Further, the thickness information is output to the outside (step S8).
The output of the thickness information is performed by, for example, a display window 30a shown in FIG. In the example shown in FIG. 9, the thickness value is displayed and output in the upper left cell 45 of the display window 30a.

As described above, the measurement result of the film thickness is output on the CRT, and is printed on a printer or stored in the image recording unit 14 as necessary.

Further, depending on the embodiment, various information shown in FIG. 9 may be measured and displayed. In the example shown in FIG. 9, a thickness display cell 45 for displaying the thickness of the region to be measured and a thickness variation display for displaying the variation of the thickness in an area designated by the position of the thickness measurement target. A cell 43, an area display cell 41 for displaying the area of the sample at the position designated by the position of the film thickness measurement object, and a defect display cell 44 for displaying the presence or absence of a defect at the position designated by the position of the film thickness measurement object. And a number counting display cell 42 for displaying the number of samples cut during operation.

In this example, the outline of the slice is specified by extracting the edge. When the edge is extracted, the edge may be emphasized by performing a spatial differentiation process or the like as a pre-process. To perform this edge extraction well,
The background portion of the section can be darker in color,
The background portion may be made of a material having characteristic reflection.

If a closed space is formed at the edge, this is labeled and treated as an intercept. Also, by performing this imaging at regular intervals and tracking the movement of the labeled slice, the number of slices can be counted.

In the rectangular section as shown in FIG. 7, if the closed space is extracted from the edge of the image and the coordinates of the four corners are specified, the area of the section can be easily obtained. Further, when the area is smaller than a certain area despite the portion surrounded by the edge, it can be determined that the slice has been folded or a defect has occurred during cutting.

The variation in the thickness can be determined based on the evaluation result by the color distribution evaluation means 8.

[0044]

According to the present invention, the color distribution evaluation means reads out the color information of the intercept measurement area for each pixel and evaluates the color distribution in the area. Then, the conversion processing unit specifies the standard color of the section from the distribution of the color evaluated by the color distribution evaluation unit and converts the color information of the specific color into thickness information. It is possible to measure the film thickness in a long time, and to measure it by converting the color information into the thickness information. In addition, since the film thickness is measured by image processing, the interference color can be treated as a digital signal, and therefore, the film thickness can be measured with extremely high accuracy compared to the case of visual observation. Excellent film thickness measuring device It is possible to provide.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a measurement unit shown in FIG.

FIG. 3 is a block diagram showing a configuration of one embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating an example of a conversion table used by a measurement unit illustrated in FIG. 3;

FIG. 5 is a block diagram illustrating a configuration of hardware resources according to the embodiment illustrated in FIG. 3;

FIG. 6 is a flowchart showing the operation of the embodiment shown in FIG.

FIG. 7 is an explanatory diagram showing an example of image data captured in step S1 shown in FIG.

8 is an explanatory diagram illustrating a setting window for setting a measurement position and the like used for specifying a section measurement area shown in FIG. 6;

FIG. 9 is an explanatory diagram showing an example of a display window used to display the measurement results shown in FIG.

[Explanation of symbols]

 2 imaging means 4 section position specifying unit 6 measuring unit 8 color distribution evaluation means 10 conversion processing means 12 error processing function 14 average color calculation function 16 error calculation function 18 error specific function

Claims (3)

[Claims] 1. An image pickup means for picking up an image of a section of a sample, a section position specifying section for specifying a region where the section is located in image data output from the image pickup section as a section measurement area, and a section position specifying section. A measurement unit that calculates the thickness of the slice based on the color information of the slice measurement region specified by the measurement unit, wherein the measurement unit calculates the color information of the slice measurement region specified by the slice position specification unit for each pixel. A color distribution evaluation unit that reads out each time and evaluates a color distribution in the area, and specifies a standard color of the intercept from the color distribution evaluated by the color distribution evaluation unit, and a color of the specified color. A film thickness measuring device, comprising: a conversion processing means for converting information into thickness information. 2. The method according to claim 1, wherein the color distribution evaluation means calculates an average color value of the color information in the intercept measurement area, and calculates an average color based on the average color calculated by the average color calculation function. An error calculation function for calculating an error for each pixel in the intercept measurement area, wherein the conversion processing means converts the color information of the pixel having the smallest error calculated by the error calculation function into a standard value of the intercept measurement area. 2. The film thickness measuring apparatus according to claim 1, further comprising: an error-specific function for setting a specific color. 3. When the color distribution evaluated by the color distribution evaluation means varies beyond a predetermined threshold, the conversion processing means stops calculating the thickness of the intercept measurement area and outputs error information. 2. The film thickness measuring apparatus according to claim 1, further comprising an error processing function for externally displaying the value.