JP2012127706A - Object size inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object size inspection method having high reliability and simple operation and suited to ordinary inspections.SOLUTION: The size of an object is inspected by whether or not a two-dimensional shape of the object passes a slit of a predetermined length that is a two-dimensional space. Image data are acquired by imaging the object, the image data are binarized, a connection area of pixels corresponding to the object is specified by the binarized binary image, contour constituting pixels are successively specified in the connection area of the pixels, one of the contour constituting pixels is adopted as a start point, a first point is moved in a first direction, a second point is moved in a second direction, and only when a straight distance between the first point and the second point is equal to or more than a specified value having a predetermined length of the slit, the second point is moved in the first direction. When the first point coincides with the second point in a state that at least either one of the first point and the second point passes all the contour constituting pixels during a period that the first point circulates all the contour constituting pixels and returns to the pixel to be the start point, passage of the two-dimensional shape of the object through the slit is determined.

Description

  The present invention relates to an object size inspection method, and more particularly to an object size inspection method suitable for inspecting the size of a micro object such as a microorganism contained in ballast water.

In order to stabilize the ship, the ship that is not loaded with cargo travels with ballast water and discharges the ballast water in the sea area where the load is loaded.
Normally, ballast water is discharged into a different sea area from the sea where it is mounted, so problems such as plankton and bacteria such as bacteria mixed in the ballast water are transported to sea areas other than the original habitat and destroy the ecosystem. There is a risk of causing.

  In order to deal with such problems, international rules regarding the regulation of ballast water have been formulated, and the “International Convention for the Regulation and Management of Ship Ballast Water and Sediment (Ballast Water Management Convention)” has been adopted. Yes.

The “Guideline for Ballast Water Sampling (G2)” related to the above Ballast Water Management Convention is based on the “Ballast Water Emission Standard (D-2)”. The number of microorganisms contained in water is defined for each category.
Further, the guideline (G2) defines that the “minimum size of microorganism” in the emission standard (D-2) means the minimum dimension of a living body excluding stab, flagellum, or touch.
Therefore, in recent years, development of ballast water treatment apparatuses has been actively conducted so as to satisfy the above emission standard (D-2).

By the way, among the microorganisms contained in the ballast water, with respect to relatively large microorganisms such as plankton, the inspection of the minimum size is performed by visual inspection by an inspector using a microscope or the like.
However, since the inspection of the minimum size by the inspector's visual inspection takes time and money, it is desired to develop a simple inspection method instead.

  In Patent Document 1, a digital image of a microorganism is acquired, and in a binary image obtained by binarizing the digital image, a pixel connection region is recognized as one microorganism, the area of the microorganism is calculated, and the calculation is performed. An elliptical minor axis having an area equal to the calculated area and an arbitrary ratio of minor axis and major axis of 1: 1.1 to 1: 8 is calculated, and the calculated minor axis is defined as the minimum size of the microorganism. An inspection method is described.

  However, the method described in Patent Document 1 assumes that the shape of the microorganism is an ellipse having the same area as that of the microorganism, and that the short diameter is the minimum size of the microorganism. The minor axis is clearly different from the definition of “minimum size” in the above guideline (G2). In addition, some microorganisms such as plankton have various shapes, but the method described in Patent Document 1 assumes that the shape is simply an ellipse, and has a large variation in measurement and reliability. It is scarce.

JP 2010-63403 A

  Accordingly, an object of the present invention is to provide an object size inspection method that is highly reliable and suitable for daily simple inspection.

  In order to achieve the above object, the object size inspection method of the present invention inspects the size of an object according to whether or not the object passes through a two-dimensional space of a predetermined dimension. The size of the object is inspected based on whether or not the two-dimensional shape passes through a slit having a predetermined length which is a two-dimensional space.

  According to the inspection method of the present invention, when the two points are moved clockwise or counterclockwise along the contour from the starting point on the contour in the two-dimensional shape of the object, the first point moves in the first direction. The second point is moved in the second direction opposite to the first direction, and the linear distance from the first point is not less than a predetermined value that is a predetermined length of the slit. The two-dimensional shape of the object passes through the slit by moving in the first direction and intersecting the second point until the first point makes a round of the outline and returns to the starting point. It is preferable to judge that.

The inspection method of the present invention acquires the image data by imaging the object,
Binarizing the image data;
Identify a connected region of pixels corresponding to the object based on the binarized binary image,
Sequentially identifying pixels constituting the contour in the connected region of the pixels,
When moving two points clockwise or counterclockwise along the pixels constituting the contour, starting from one of the pixels constituting the contour, the first point is moved in the first direction, The second point is moved in the second direction opposite to the first direction, and the first point is only when the linear distance from the first point is equal to or greater than a predetermined value which is a predetermined length of the slit. And moving all the pixels constituting the contour to the first point and the second time until the first point makes a round of pixels constituting the contour and returns to the starting pixel. It is preferable to determine that the two-dimensional shape of the object passes through the slit by matching the first point and the second point when at least one of the points has passed.

  The second point moves in the second direction within a range in which the linear distance from the first point is less than the specified value every time the first point is moved by one pixel in the first direction. Or moving in the first direction until the linear distance to the first point is less than the specified value.

  Furthermore, it is preferable that the image data of the object is captured and acquired by a scanner.

  In the inspection method of the present invention, the object is preferably a microorganism.

  In the object size inspection method according to the present invention, the size of the object is inspected based on whether or not the object passes through a two-dimensional space of a predetermined size, that is, whether the size of the object is equal to or larger than the predetermined size. Specifically, depending on whether or not the two-dimensional shape of the object passes through a slit of a predetermined length which is a two-dimensional space, the size of the object is inspected, or the three-dimensional shape of the object is two-dimensional space. Since the size of the object is inspected depending on whether or not it passes through a circle having a predetermined diameter, it is highly reliable and suitable for simple and daily inspection.

  In the inspection method of the present invention, when the two points are moved clockwise or counterclockwise along the contour from the starting point on the contour in the two-dimensional shape of the object, the first point is the first direction. When the second point is moved in the second direction opposite to the first direction and the linear distance from the first point is equal to or greater than a predetermined value which is a predetermined length of the slit. Only in the first direction, and the first point makes a round of the outline and coincides with the second point until it returns to the starting point. If it is determined that the object passes, it is possible to inspect whether or not the size of the object is equal to or larger than a predetermined value by a simple operation of tracing the outline of the object.

  Furthermore, in the inspection method of the present invention, the object is imaged to acquire image data, the image data is binarized, and a pixel corresponding to the object is detected based on the binarized binary image. Specify a connected region, sequentially specify pixels constituting the contour in the connected region of the pixels, and start one of the pixels constituting the contour as a starting point and rotate two points clockwise or along the pixels constituting the contour When moving counterclockwise, the first point is moved in the first direction, the second point is moved in the second direction opposite to the first direction, and a straight line with the first point. Only when the distance is equal to or greater than a predetermined value that is the predetermined length of the slit, the first direction is moved until the first point goes around the pixels constituting the contour and returns to the pixel that is the starting point. Between all the pixels constituting the contour in the first point If it is determined that the two-dimensional shape of the object passes through the slit by matching the first point and the second point when at least one of the second points has passed. It is possible to easily and accurately inspect whether or not the size of the object is equal to or larger than a specified value using an image processing technique.

  Here, the inspection method of the present invention is suitable for daily simple inspection if the image data of the object is acquired by a scanner.

  And if the said object is a microorganism, the test | inspection method of this invention can test | inspect the minimum size of the microorganisms contained in ballast water easily accurately.

An example of plankton images with a fluorescence microscope. Flow chart of size inspection method. The image figure of a binary image. Explanatory drawing of a raster scan. Explanatory drawing of a contour tracking method. The figure which attached the outline number in order of outline tracking in FIG. The flowchart of size determination. FIG. 1 is an explanatory diagram 1 of the first embodiment. FIG. 2 is an explanatory view of the first embodiment. FIG. 3 is an explanatory diagram of the first embodiment. FIG. 4 is an explanatory diagram of the first embodiment. FIG. 5 is an explanatory diagram of the first embodiment. The image figure of a binary image. FIG. 1 is an explanatory diagram of a second embodiment. FIG. 2 is an explanatory diagram of the second embodiment. FIG. 3 is an explanatory diagram of the second embodiment. FIG. 4 is an explanatory diagram of the second embodiment. FIG. 5 is an explanatory diagram of the second embodiment.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of fluorescence microscope images of various planktons to be inspected in the embodiment of the present invention.
FIG. 1 (a) shows images of barnacle larvae (zooplankton), (b) shows copepods (zooplankton), and (c) and (d) show diatoms (phytoplankton).
In each image, a portion indicated by an arrow corresponds to “minimum size of microorganism” defined in the guideline (G2) of the Ballast Water Management Convention.

Here, in the embodiment of the present invention, the “minimum size” of the plankton is assumed to be the minimum size of the slit length through which the planar shape of the plankton in the image can pass.
Then, the inspection method for the “minimum size” of plankton in the embodiment of the present invention is based on whether or not the connected region of the pixels corresponding to the plankton in the image can pass through a slit having a specified length. It is intended to determine whether or not the minimum size of plankton is not less than a specified length.

FIG. 2 shows the flow of the plankton minimum size inspection method.
In the present embodiment, the inspection of the minimum size of the blankton is performed in the imaging step (S1), the binarization processing step (S2), the labeling step (S3), the contour tracking step (S4), and the size determining step (S5). It goes through each process.

(1) Imaging process: S1
In this step, the sample of the ballast water sample is scanned and imaged with a scanner to obtain plankton image data.
Here, if plankton is dyed in advance, it becomes easy to determine the plankton in the image data. In addition, if a dye that stains only living cells is used, it becomes easy to discriminate living plankton having living cells in the image data.
Then, if the plankton live cells are fluorescently stained with a known fluorescent dye in advance, the live plankton having the live cells can be imaged by a fluorescent image scanner.

(2) Binarization process: S2
In this step, the image data acquired in the imaging step (S1) is binarized to obtain a binary image.
Here, FIG. 3 shows an image of a binary image acquired by the binarization processing. A plurality of white or black squares in FIG. 3 each indicate a pixel. In FIG. 3, pixels corresponding to plankton are shown in white.

(3) Labeling process: S3
In this step, a pixel region corresponding to plankton is identified from the binary image acquired in the binarization processing step (S2) by a technique such as raster scanning so that each pixel region can be distinguished. Perform labeling.
Here, the pixel region is a single pixel region in which one pixel having a pixel value 1 is independent or a connected region in which a plurality of pixels having a pixel value 1 are connected.
The example shown in FIG. 3 shows a connected region of pixels corresponding to plankton.

(4) Outline tracking step: S4
In this step, the connected region of the pixels specified in the labeling step (S3) starts from one of the pixels (contour pixel) constituting the contour, and the contour of the connected region is tracked in units of pixels. Here, the outline in the present embodiment refers to the outer outline of the connected area of the pixels.
At this time, the first contour pixel as the starting point can be specified by, for example, raster scanning. The contour can be tracked by a known method such as 4-neighbor tracking or 8-neighbor tracking for obtaining a boundary of connected pixels.

FIG. 4 shows an example of searching for the first contour pixel by raster scanning in the binary image shown in FIG. Raster scanning is a scanning technique in which an upper left corner of an image is used as a starting point, pixels are examined from the left end to the right, and once arrived at the right end, one row is moved down and pixels are examined from the left end to the right.
FIG. 5A shows a method for tracking an outline by the 4-neighbor tracking, and FIG. 5B shows a method for tracking an outline by the 8-neighbor tracking. Each neighborhood tracking shown in FIGS. 5A and 5B is a method of searching for the next contour pixel in the numerical order shown in the clockwise direction from the tracking direction around the searched contour pixel O.

In the present embodiment, in the pixel connection region, the first contour pixel is specified by raster scanning, and the contour pixel is sequentially searched from the first contour pixel in the clockwise direction by tracking eight neighbors. The tracking of the contour ends when the searched pixel is the first contour pixel and the pixel to be searched next is a searched pixel.
6 shows that the first contour pixel in the binary image shown in FIG. (1), and contour numbers (contour No. (2) to No. (16)) are assigned in the order of contour pixel tracking.

(5) Size determination step: S5
In this step, it is determined whether or not the minimum size of plankton corresponding to the connected region is greater than or equal to a specified length for the connected region in which the contour pixel is specified in the contour tracking step (S4).
In the present embodiment, in the binary image shown in FIG. (1) is a starting pixel A, and two points B and C from the starting pixel A are moved along the contour pixels in the order of the contour numbers.

For the first point B, the contour No. (1) → No. (2) → No. (3) Move in the first direction in the clockwise direction. For the second point C, the contour No. (1) → No. (16) → No. (15) → ... and move it counterclockwise in the second direction.
Here, for the second point C, each time the first point B is moved to a pixel of the next contour number, the distance from the first point B is within a range less than the specified length, It is continuously moved in the second direction in the order of contour numbers. When the distance to the first point B is equal to or longer than the specified length, the distance is continuously moved in the first direction in the order of the contour numbers until the distance is less than the specified length. .

  Then, the first point B goes around the contour pixels in the order of the contour numbers, and the contour No. When the first point B and the second point C intersect with pixels having the same contour number before returning to the starting pixel A in (1), that is, all of the contour pixels are When the first point B and the second point C coincide with each other when at least one of the point B and the second point C has passed, the connecting region can pass through a slit having a specified length. As described above, it is determined that the minimum plankton size corresponding to the connected area is less than the specified length.

  On the other hand, the first point B goes around the contour pixel without matching with the pixel having the same contour number as the second point C. Returning to the starting pixel A in (1), it is determined that the minimum size of the plankton corresponding to the connection region is not less than the predetermined length, because the connection region cannot pass through the slit having the predetermined length.

  Hereinafter, determination of “minimum size” of plankton in the present embodiment will be described based on examples.

<Example of judging that the minimum plankton size is less than the specified length>
FIG. 7 shows a flowchart for determining the minimum size of plankton using image processing. 8 to 12 show examples in which the flowchart shown in FIG. 7 is applied to the binary image shown in FIG. 8A to 12B, (a) shows an image of a binary image, and (b) shows a contour list created based on the contour numbers shown in FIG.
In this embodiment, the distance between the points B and C (distance between BC points) is the distance between the pixel centers where the points are located. The specified length is 2.5 pixels.

  First, as shown in FIG. (1) is determined as the starting pixel A. At this time, since both the points B and C are located on the starting pixel A, the distance between the BC points is 0.0 pixels as shown in the outline list of FIG. 8B.

  Next, the points B and C are moved in the order of the contour numbers. First, as shown in FIG. (1) → No. (2) Move one pixel clockwise in the first direction. In this case, as shown in the outline list of FIG. 9B, since the distance between BC points is 1.0 pixel, it is determined that the distance is less than the specified length. (1) → No. (16) and move one pixel counterclockwise in the second direction. In this case, as shown in the outline list of FIG. 10B, since the distance between the BC points is 1.4 pixels, it is determined that the distance is less than the specified length. No. (15) and one pixel are moved in the second direction.

  Thereafter, until it is determined that the distance between the BC points is equal to or longer than the specified length, the C point is set to the contour No. in accordance with the contour list. (15) → No. (14) → No. (13) →... And continuously moved in the second direction. Then, as shown in FIG. When moved to (12), as shown in the outline list of FIG. 10 (b), if the distance between BC points is 3.2 pixels and it is determined that the distance is equal to or longer than the specified length, then as shown in FIG. Point is contour no. (12) → No. In contrast to (13), one pixel is moved clockwise in the first direction. Then, as shown in the outline list of FIG. 11B, since the distance between BC points is 2.2 pixels, it is determined that the distance is less than the specified length. (2) → No. (3) and move one pixel in the first direction.

  The movement of point B and point C is repeated as described above, and as shown in FIG. (7) → No. (8) and move one pixel in the first direction. In this case, as shown in the outline list of FIG. (12) → No. (11) → No. (10) → No. (9) → No. (8) and move continuously in the second direction.

  Thus, in the present embodiment, the points B and C are contour Nos. Matches at pixel (8). Therefore, in this embodiment, it is determined that the minimum size of the plankton corresponding to the binary image connection area shown in FIG. 3 is less than the specified length.

<Example of determining the minimum plankton size to be longer than the specified length>
FIG. 13 shows an image of a binary image used in this embodiment. In the binary image shown in FIG. 13, the first contour pixel is added to the contour pixel searched in the contour tracking step (S4). As (1), contour numbers (contour Nos. (2) to No. (16)) are given in the order of tracking.
14 to 18 show an example in which the flow shown in FIG. 7 is applied to the binary image shown in FIG. In each of FIGS. 14 to 18, (a) shows an image of a binary image, and (b) shows a contour list created based on the contour number shown in FIG. 13.
In this embodiment as well, the distance between BC points is the distance between the pixel centers where each point is located. The specified length is 2.5 pixels.

  First, as shown in FIG. (1) is determined as the starting pixel A. At this time, since both the points B and C are located on the starting pixel A, the distance between the BC points is 0.0 pixels as shown in the outline list of FIG.

  Next, the points B and C are moved in the order of the contour numbers. First, as shown in FIG. (1) → No. (2) Move one pixel clockwise in the first direction. In this case, as shown in the outline list of FIG. 15B, since the distance between BC points is 1.0 pixel, it is determined that the distance is less than the specified length. (1) → No. (16) and move one pixel counterclockwise in the second direction. In this case, as shown in the outline list of FIG. 15B, since the distance between the BC points is 1.4 pixels, it is determined that the distance is less than the specified length. (16) → No. (15) and move one pixel in the second direction.

  Thereafter, until it is determined that the distance between the BC points is equal to or longer than the specified length, the C point is set to the contour No. in accordance with the contour list. (15) → No. (14) → No. (13) →... And continuously moved in the second direction. Then, as shown in FIG. When it is moved to (12), as shown in the contour list of FIG. 15B, if it is determined that the distance between BC points is 3.2 pixels and is not less than the specified length, then the C point is contour No. (12) → No. In contrast to (13), one pixel is moved clockwise in the first direction. Then, since the distance between BC points is 2.2 pixels, it is determined that the distance is less than the specified length. (2) → No. (3) and move one pixel in the first direction.

  The movement of point B and point C is repeated as described above, and as shown in FIG. (4) → No. (5) and move one pixel in the first direction. In this case, as shown in the outline list of FIG. Since the distance between the BC points is 2.8 pixels, it is determined that the distance between the BC points is equal to or longer than the specified length. (13) → No. (14) → No. (15) → No. (16) → No. (1) → No. (2) → No. (3) and move continuously in the first direction.

  Further, the movement of points B and C is repeated as described above, and as shown in FIG. (15) → No. (16) and move one pixel in the first direction. In this case, as shown in the outline list of FIG. 17B, the C point is set to the outline No. until the distance between the BC points is determined to be less than the specified length. (7) → No. (8) → No. (9) → No. (10) → No. (11) → No. (12) → No. (13) and move continuously in the first direction.

  Then, as shown in FIG. (16) → No. (1) and move one pixel in the first direction.

  As described above, in this embodiment, the point B goes around the contour pixel without crossing the points B and C at the pixel having the same contour number, and the contour No. Return to the starting pixel A in (1). Therefore, in this embodiment, it is determined that the minimum size of plankton corresponding to the binary image connection area shown in FIG.

  In the first and second embodiments, it is assumed that the contour of the connected region of the image is a line connecting the centers of the contour pixels, and the distance between BC points is the distance between the pixel centers where the points are located. Assuming that the contour of the connected region is a line connecting the vertices in the outermost contour of the contour pixel, the distance between the BC points is the distance using the vertices of the four corners of the pixel where each point is located. It is possible to accurately determine the minimum plankton size.

  The above embodiment of the present invention assumes that the “minimum size” of plankton is the minimum size of the slit length through which the planar shape of the plankton can pass, and the planar shape of the plankton has a predetermined length. It is intended to determine whether or not the minimum size of the plankton is greater than or equal to a predetermined length depending on whether or not it can pass through the slit. By repeating the inspection, the minimum size of the plankton itself can be obtained.

  In the embodiment of the present invention described above, whether or not the plankton plane shape can pass through a slit having a predetermined length, which is a two-dimensional space, determines whether or not the minimum size of the plankton is not less than a predetermined length. If the plankton's three-dimensional shape can be identified, whether or not the minimum size of the plankton is equal to or larger than the predetermined size depends on whether or not the three-dimensional shape can pass through a circle having a predetermined diameter in a two-dimensional space. Can be determined with higher accuracy.

  Although the above embodiment of the present invention is for inspecting the minimum size of plankton, it is obvious that it can be applied to the inspection of the minimum size of other microorganisms and the sizes of other various objects.

  It goes without saying that the present invention is not limited to the above-described embodiment, and the configuration thereof can be changed as appropriate without departing from the scope of the invention.

  The object size inspection method of the present invention has high reliability, is simple and suitable for daily inspection, and has extremely high utility value.

Claims (6)

  An object size inspection method for inspecting the size of an object depending on whether or not the two-dimensional shape of the object passes through a slit having a predetermined length in a two-dimensional space.   When moving two points clockwise or counterclockwise along the contour from the starting point on the contour in the two-dimensional shape of the object, the first point is moved in the first direction, and the second point is Move in the second direction opposite to the first direction and move in the first direction only when the linear distance from the first point is equal to or greater than a specified value that is the predetermined length of the slit. The two-dimensional shape of the object is determined to pass through the slit by matching the second point before the first point makes a round of the outline and returns to the starting point. The minimum size inspection method for the described object. Image the object to obtain image data;
Binarizing the image data;
Identify a connected region of pixels corresponding to the object based on the binarized binary image,
Sequentially identifying pixels constituting the contour in the connected region of the pixels,
When moving two points clockwise or counterclockwise along the pixels constituting the contour, starting from one of the pixels constituting the contour, the first point is moved in the first direction, The second point is moved in the second direction opposite to the first direction, and the first point is only when the linear distance from the first point is equal to or greater than a predetermined value which is a predetermined length of the slit. And moving all the pixels constituting the contour to the first point and the second time until the first point makes a round of pixels constituting the contour and returns to the starting pixel. 3. The two-dimensional shape of the object is determined to pass through the slit by matching the first point and the second point in a state where at least one of the points has passed. 4. Object size inspection method.   Each time the second point is moved one pixel in the first direction in the first direction, the linear distance from the first point is moved in the second direction within a range less than the specified value, The object size inspection method according to claim 3, wherein the object is moved in the first direction until a linear distance to the first point becomes less than the specified value.   5. The object size inspection method according to claim 3 or 4, wherein the image data of the object is captured and acquired by a scanner.   The method for inspecting the size of an object according to any one of claims 1 to 5, wherein the object is a microorganism.

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