KR100765047B1 - Portable concrete surface crack detecting apparatus with image processing and method thereof - Google Patents

Abstract

A portable concrete surface crack measuring device and method using image processing are provided to measure the width of a crack easily and reliably and to build up a database simply. A portable concrete surface crack measuring device(1) comprises a distance measuring unit(20), a camera(30), an indication unit(40), a setting unit(50), and a calculation unit(60). The distance measuring unit measures a distance to an inspection object. The camera takes a picture of the inspection object. The display unit displays the image of the camera. The setting unit sets at least two points of a crack portion in the image. The calculation unit computes the actual distance between the set points on the basis of the distance to the inspection object.

Description

PORTABLE CONCRETE SURFACE CRACK DETECTING APPARATUS WITH IMAGE PROCESSING AND METHOD THEREOF

1a and 1b is a front view and a rear view of a portable concrete surface crack measurement apparatus according to the present invention

2 is a block diagram of a portable concrete surface crack measurement apparatus according to the present invention

3 is a view illustrating the operation of the portable concrete surface crack measurement apparatus according to the present invention

Figure 4 is a flow chart for explaining an embodiment of a portable concrete surface crack measurement method according to the invention

5 illustrates an example of a screen displayed on a display unit during the process of FIG. 4.

6 is an exemplary view of a screen displayed on the display in the case of another embodiment of a portable concrete surface crack measurement method according to the present invention

7 is a distribution diagram of pixel values displayed on a display unit in the embodiment of a portable concrete surface crack measurement method according to the present invention;

8 is an exemplary view of a screen displayed on the display in the case of another embodiment of a portable concrete surface crack measurement method according to the present invention

FIG. 9 is a distribution diagram of pixel values of pixels in the region 103 of FIG. 8.

10A and 10B are exemplary views of images in which light effects are not corrected and images in which light effects are corrected by a morphology technique.

11A and 11B are graphs showing pixel values of pixels located along the A-A line in FIGS. 10A and 10B, respectively.

<Explanation of symbols for main parts of the drawings>

10: lighting device 20: distance meter

30: camera 40: display unit

50: command input device 60: control unit

70: video storage device 80: external transceiver

The present invention relates to a portable concrete surface crack measuring apparatus and method, and more particularly to a device and method for measuring the width of the concrete surface by performing a digital image processing of the concrete surface image taken by the camera.

Concrete structures commonly used in buildings, tunnels, bridges, etc., are damaged and aged over time. In order to maintain the function of the damaged and aged concrete structure to prolong its life, it is necessary to continuously manage and inspect the concrete structure.

In the inspection of concrete structures, the most basic investigation is the appearance investigation, and the investigation of the crack on the surface of the concrete structure in the exterior investigation is an important factor in determining whether or not to perform the precise safety diagnosis of the concrete structure.

Investigation of cracks in the surface of concrete structures has usually been made by visual observation. However, visual observation has a disadvantage in that it is difficult to measure objective crack width due to the subjectivity of the measurer and has low reliability. In addition, when it is difficult for the measurer to access the concrete structure, the measurement efficiency is lowered and the risk of a safety accident follows.

In this aspect, the crack measurement method of the surface of the concrete structure by the imaging technique is a trend. Korean Patent Laid-Open Nos. 2002-77250 and 2004-20261 disclose an apparatus and method for measuring cracks by processing an image of a concrete structure. However, these devices are mounted on vehicles or on their own mobile vehicles, making it difficult for the user on site to measure cracks in the concrete structure surface in real time according to site conditions.

In order to overcome the above-mentioned problems, an object of the present invention is to provide a concrete surface crack measuring apparatus and method that can be carried by the user and can measure the crack of the surface of the concrete structure by image processing.

In order to achieve this object, the present invention, the distance measurer for measuring the distance to the inspection object; A camera for photographing an inspection object; A display unit displaying an image of a camera; Designation means for designating at least two or more points of the crack portion in the image displayed by the display portion; And calculating means for calculating an actual distance between the points designated by the designation means based on the distance to the inspection object measured by the distance measurer.

Such a measuring device may further include a lighting device for illuminating the inspection object.

Such a measuring device may further include transmitting and receiving means for transmitting and receiving the image and the information about the image.

For the case of inspecting the inspection object in the tilted direction, the distance measurer measures the distance to at least three points which do not constitute a straight line on the inspection object, and the calculation means is based on the distance to the measured at least three points. It is preferable to include a correction means for calculating the inclination angle of the inspection object with respect to the optical axis of the camera and correcting the actual distance based on the inclination angle. In this case, the display unit may display an image corrected based on the inclination angle.

In addition, the present invention, the distance measuring step of measuring the distance to the inspection object; A focus adjusting step of adjusting a focus of the camera according to the measured distance; A photographing step of photographing an image of an inspection target by a camera; An image display step of displaying the captured image on a display screen; A length calculation step of calculating an actual length between the plurality of points in the image displayed on the display screen based on the distance measured in the distance measuring step; And a length display step of displaying an actual length on a display screen.

In the image displayed on the display screen, statistics of pixel values are calculated for a predetermined area designated by the user, the crack area of the inspection target is defined based on the statistics, and the image and the crack area are displayed on the display screen, or the display screen The distribution of pixel values is displayed on the display screen for the entire image or a predetermined area designated by the user on the display screen, and the crack area of the inspection target is defined based on the predetermined value specified by the user in the distribution of pixel values. Allows you to display images and defined crack areas on the screen.

In addition, a morphology technique may be applied to make the background brightness of the captured image uniform. The morphology technique is preferably a technique of subtracting a photographed image from an image that performs a closed operation on the photographed image.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the configuration of the apparatus according to the present invention is described. 1A and 1B are front and rear views of a portable concrete surface crack measuring apparatus 1 according to the present invention, and FIG. 2 is a block diagram thereof.

As illustrated in FIGS. 1A, 1B and 2, the crack measuring apparatus 1 according to the present invention includes a lighting device 10, a distance measuring device 20, a camera 30, a display unit 40, and a command input device 50. , The controller 60, the image storage device 70, and the external transceiver 80. The crack measuring device 1 is a size that a user can carry with one hand, and may be a separate device having a size similar to that of a PDA or a mobile phone, or may be used by mounting an external device and a program suitable for a PDA or a mobile phone. 3 is an exemplary view of the operation of photographing the crack of the concrete surface using the crack measuring device (1).

The lighting device 10 is a device for illuminating the concrete surface to be inspected and is located in front of the crack measuring device 1. The lighting device 10 may be configured to be operated by the user when the concrete surface is dark or to be automatically operated when the brightness measured by a separate sensor or the camera 30 to be described below is equal to or less than a predetermined value.

The distance measuring device 20 is located in front of the crack measuring device 1 and measures the distance from the crack measuring device to the concrete surface to be inspected along the optical axis of the camera 30 to be described later. The range finder 20 uses infrared rays or the like as used in a general auto focus camera. The optical axis of the range finder 20 coincides with the optical axis of the camera 30, and the range finder 20 is located close to the camera 30 on the crack measuring device in order to reduce the error of the measured distance. The measured distance is output to the controller 60 to be described later.

If the optical axis of the camera 30 to be described later and the concrete surface to be inspected are not vertical, the image measured by the camera 30 is distorted, and the actual length represented by each pixel in the image is determined by the position of the pixel in the image. Will change accordingly. In order to correct this distortion and obtain an accurate actual length, information on the inclination angle between the optical axis of the camera 30 and the concrete surface is required. Therefore, the distance meter 20 preferably measures the distance with respect to three or more points which are not located in a straight line on the concrete surface to be inspected in order to measure this inclination angle. For example, the distance measurer 20 may measure a distance between two points spaced apart by a predetermined angle in the horizontal and vertical directions from the point where the optical axis and the concrete surface of the camera 30 meet and the point where the optical axis and the concrete surface meet. Can be.

The camera 30 is located in front of the crack measuring device 1. The camera 30 includes an imaging lens, an imaging device such as a CCD or a CMOS, a focus control device, and the like. The focus of the camera 30 is adjusted by the distance measured by the range finder 20. The image photographed by the camera 30 is output to the controller 60.

The display unit 40 is located on the rear surface 1 of the crack measuring device. The display unit 40 is a crack measuring device control screen, an image captured by the camera 30 or read from an image storage device 70 to be described later, or input through an external transceiver 80, data on a concrete surface and cracks thereof. And so on.

The command input device 50 includes a keypad for inputting letters, numbers, and the like, a photographing key, a storage key, and a mouse, and is located at the rear of the crack measuring device 1. Alternatively, the command input device 50 may be located together with the display unit 40 in a touch screen manner.

The control part 60 is built in the crack measuring apparatus 1. The control unit 60 includes a CPU, a ROM, a RAM, and the like. The control unit 60 controls each part of the crack measuring device 1 according to the command input to the command input device 50 and performs calculation for crack measurement.

More specifically, the control unit 60 allows the distance measuring device 20 to measure the distance from the crack measuring device to the concrete surface to be inspected when the crack measuring operation start command is input from the command input device 50. The measured distance is stored in the RAM in the controller 60, and the controller 60 controls the focus of the camera 30 based on the measured distance, and the image photographed by the camera 30 is input to the controller 60. The controller 60 outputs an image to the display unit 40. When the user designates two points corresponding to the boundary of the crack in the output image to measure the width of the crack on the concrete surface to be inspected using the mouse of the command input device 50, the controller 60 controls the user. Read the pixel coordinates corresponding to the location specified by the to calculate the pixel length between the two points, and calculate the width of the actual crack using the calculated pixel length and the distance from the distance meter 20 to the input concrete surface.

In addition, when the distance measurer 20 measures the distance with respect to three or more points which are not located in a straight line on the concrete surface, the controller 60 uses the measured distance to the plurality of points to determine the distance of the camera 30. Calculate the angle of inclination of the optical axis and the concrete surface, and calculate the width of the actual crack between two user-specified points by correcting the distortion caused by the slope if the angle is not 90 ° (non-vertical). When the image of the display unit 40 is severely distorted, the controller 60 may correct the tilted angle of the image input from the camera 30 and output the image to the display unit 40 according to the user's selection.

Image storage device 70 is composed of a hard disk or flash RAM, etc., the image taken by the camera 30 or input through the external transceiver 80, the recording time, the location of shooting, the cracking of each measurement position It is stored in the crack measuring device 1 in order to store it along with additional information about the image including the width, its average and maximum values, and the user's comment and the like, and to read the stored image when the user needs it.

The external transceiver 80 is used to output the image photographed by the crack measuring device and additional information about the image to the outside via wired or wireless, and input necessary data from the outside. The external transceiver 80 may use an external interface such as a pin connector, a USB connector or a wired or wireless LAN card. In addition, the external transceiver 80 may have a function such as a radio, a mobile phone.

Next, the Example of the method of measuring the crack of a concrete surface with the portable concrete surface crack measuring apparatus 1 comprised as mentioned above is described in detail. 4 is a flowchart for explaining an embodiment of the method according to the present invention.

The user inputs information of an object to be measured using the command input device 50. In the information, a detection target, a location, a time, and user information are input (step S10). Some of these may be automatically input by the crack measuring apparatus 1. When the input is completed, the user presses the shooting key to perform the test.

The controller 60 drives the distance meter 20 according to a user's command. The distance measurer 20 measures the distance to the inspection object and outputs the measured distance to the control unit 60 (step S11), and the controller 60 stores the measured distance and adjusts the focus of the camera 30 according to the measured distance. (Step S12). The focus-adjusted camera 30 photographs a test object and outputs an image to the controller 60 (operation S13).

The controller 60 displays the captured image on the display unit 40 (step S14). 5 is an exemplary diagram of a captured image 100 displayed on the display unit 40. The crack on the concrete surface of the photographed image 100 is represented by '101'. The user may move the arrow on the display unit 40 using a mouse of the command input device 50. The user moves the arrow to the position where the width of the crack 101 is to be measured, and clicks and designates two opposite points A and B on the boundary of the crack 101 in sequence (step S15).

The controller 60 calculates the length in pixels of the image between the two points A and B designated by the user. The controller 60 converts the pixel unit into the actual length by using the distance to the inspection target measured in step S11 (step S16). The actual width of the calculated crack is displayed on the display unit 60 (step S17).

The width of the crack calculated at the specific position of the captured image and the image is displayed on the display unit, and may be stored in the storage device 70 or output to the outside through the external transceiver 80 according to a user's selection.

In addition, in step S11 of FIG. 4, the distance measurer 30 may measure the distance from the crack measuring apparatus for three or more points that do not form a straight line on the inspection target surface. The controller 60 calculates and stores an inclination angle between the optical axis of the camera 30 and the inspection target surface using the measured distances to three or more points. When the controller 60 calculates the actual width of the crack in step S17, the length calculated by the length in pixels and the distance to the inspection target is corrected using the inclination angle calculated in step S11. In addition, the display unit 40 displays the calculated and corrected width of the crack in step S18. Alternatively, the image in which the inclination angle is corrected in operation S15 may be output to the display unit 40 according to the user's selection.

Although it has been described above that the user visually designates the position of the crack 101 in the captured image 100 displayed on the display unit 40 (step S15), the crack 101 may be automatically designated by the crack measuring device.

6 illustrates a screen of the display unit 40 for explaining an embodiment of a method of automatically designating a crack region 101 in the crack measuring apparatus. The image 100 captured by the camera 30 is output to the display unit 40. The user designates an arbitrary region 102 without a crack on the image 100 as a mouse of the command input device 50. The controller 60 calculates a distribution of pixel values of pixels in the designated area 102. For example, in 8 bit (0 to 255) black and white mode, the pixel value will be between black (0) and white (255), and the pixel value of the crack will be Will be low. The control unit 60 calculates at least one of a minimum value, an average value, a median value, or a mode value of the pixel values in the designated area 102, and sets the reference value by subtracting the pixel value from the reference value or the pixel value from the reference value. Pixels having a value equal to or greater than a predetermined number are automatically defined as pixels in the crack region 101. Then, a pixel defined as a pixel in the crack area and a boundary of the pixels are displayed on the image 100 on the display unit 40. The user may designate the position where the width is to be measured directly as shown in FIG. 5 or automatically calculate the length, width, width, etc. for the crack area 101 thus defined.

FIG. 7 illustrates a screen of the display unit 40 for explaining another embodiment of a method of automatically designating a crack region in the crack measuring apparatus. The screen of the distribution diagram 200 of pixel values of each pixel of the image photographed by the camera 30 is displayed on the display unit 40 with the horizontal axis as the pixel value and the vertical axis as the number. In the absence of cracks, the concrete surface will be close to white and the pixel value distribution curve 201 on the distribution map 200 will have one peak on the right. However, if there is a crack, the cracked portion will be close to black, and the pixel value distribution curve 201 on the distribution map 200 will be a curve with two peaks on the right side of the intact portion and the left side of the cracked portion. The user moves the straight line 202 defining the boundary between the pixel value of the undamaged portion and the cracked portion with an arrow or a mouse or the like on the command input device 50 and designates an appropriate position of the straight line 202. When the position of the straight line 202 is specified, pixels having a pixel value lower than the pixel value designated by the straight line 202, that is, pixels located to the left of the straight line 202, are designated as the crack regions. The display unit 40 switches the display to the photographed image 100 of FIG. 5 or 6, and the designated pixels are displayed as the crack area 101 on the photographed image 100, so that the user can confirm the display. The user may designate the position where the width is to be measured directly as shown in FIG. 5 or automatically calculate the length, width, width, etc. for the crack area 101 thus defined.

8 and 9 illustrate screens of the display unit 40 for explaining another embodiment of a method of automatically designating a crack area in the crack measuring apparatus. In FIG. 8, an image 100 photographed by the camera 30 is output to the display unit 40. The user designates a region 103 having a predetermined size smaller than the entire image 100 of the display unit 40 including the crack portion 101. Similar to FIG. 7, a screen of a distribution diagram 200 ′ of pixel values of each pixel of the region 103 designated in FIG. 9 is displayed on the display unit 40 with the horizontal axis as the pixel value and the vertical axis as the number. The user moves the straight line 202 'defining the boundary between the pixel value of the undamaged portion and the cracked portion with an arrow or a mouse on the command input device 40 and designates an appropriate position of the straight line 202'. Pixels having pixel values lower than the pixel values designated by the straight line 202 'are designated as crack regions. The display unit 40 switches the display to the photographed image 100 of FIG. 8, and designated pixels are displayed as crack regions. Compared to a method of designating a crack region using pixel values of the entire region described with reference to FIGS. 6 and 7, a method of designating a crack region using pixel values of the region regions described in FIGS. 8 and 9 The influence of such a change can be suppressed when the pixel value of the cracked area or the pixel value of the intact area changes in the entire image 100.

On the other hand, the brightness of the concrete surface for each location may not be constant due to the influence of lighting when shooting. The present invention proposes a morphology technique for correcting the influence of the brightness of the light at the non-constant position. This morphology technique is automatically applied after the examination subject shooting (step S13 of FIG. 4) or selectively when the user determines that the brightness of the background is not constant after displaying the photographed image on the display unit (step S14 of FIG. 4). Can be applied.

The morphology technique is basically based on four operations: erosion, dilation, opening and closing. In order to make the brightness of the background uniform, as shown in Equation 1, a technique of performing a closed operation on the image and then subtracting the original image from the image on which the operation is performed is preferable.

’ 및 ‘

’는 각각 팽창 및 침식 연산, 그리고 ‘·’은 폐쇄 연산을 나타낸다. In Equation 1, 'A' is the original image, 'B' is the kernel used for the expansion and erosion operation, 'C' is the image where the influence of non-uniform light is removed,

'And'

'Represents expansion and erosion operations, respectively, and' · 'represents closure operations.

10A and 10B show a crack image in which the influence of light is not corrected and a crack image in which the influence of light is corrected, respectively. 11A and 11B show pixel values of pixels located along the A-A line of FIGS. 10A and 10B, respectively. As shown in FIGS. 10A to 11B, when the morphology technique is applied to an image having a constant brightness and a tilted image (FIGS. 10A and 11A), the brightness of the background may be uniform (FIGS. 10B and 10B). 11B).

As described above, the present invention provides a concrete surface crack measuring apparatus and method that can be carried by the user and can measure the crack of the surface of the concrete structure by image processing. According to the present invention, the crack width can be easily and reliably measured, and the database can be easily constructed.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it will be readily apparent to those skilled in the art that various other modifications and variations are possible without departing from the spirit and scope of the present invention. It is obvious that all belong to the scope of the appended claims.

Claims (12)

delete delete delete A range finder for measuring a distance to an inspection object; A camera photographing the inspection object; A display unit which displays an image of the camera; Designation means for designating at least two or more points of the crack portion in the image displayed by the display portion; And Calculation means for calculating an actual distance between points designated by the designation means based on the distance to the inspection object measured by the distance measurer; The range finder measures a distance to at least three points that do not form a straight line on the inspection object, and The calculating means includes correction means for calculating an inclination angle of the inspection object with respect to the optical axis of the camera based on the measured distances to the at least three points, and correcting the actual distance based on the inclination angle. Portable concrete surface crack measurement apparatus by image processing. The apparatus of claim 4, wherein the display unit displays an image corrected based on the inclination angle. 6. delete A distance measuring step of measuring a distance to an inspection object; A focus adjusting step of adjusting a focus of the camera according to the measured distance; A photographing step of photographing an image of the inspection target by the camera; An image display step of displaying the photographed image on a display screen; A length calculation step of calculating an actual length between a plurality of points in the image displayed on the display screen based on the distance measured in the distance measuring step; And A length display step of displaying the actual length on the display screen; Statistical values of pixel values are calculated for a predetermined area designated by a user in the image displayed on the display screen, and a crack area of the inspection target is defined based on the statistical value, and the image and the crack area are displayed on the display screen. The concrete surface crack measurement method by the image processing, further comprising the crack display step of displaying. A distance measuring step of measuring a distance to an inspection object; A focus adjusting step of adjusting a focus of the camera according to the measured distance; A photographing step of photographing an image of the inspection target by the camera; An image display step of displaying the photographed image on a display screen; A length calculation step of calculating an actual length between a plurality of points in the image displayed on the display screen based on the distance measured in the distance measuring step; And A length display step of displaying the actual length on the display screen; A pixel value distribution display step of displaying a distribution of pixel values on an entire display screen or a predetermined area designated by a user among the images displayed on the display screen; And And a crack display step of defining a crack area of the inspection target based on a predetermined value designated by a user in the distribution of pixel values, and displaying the image and the prescribed crack area on the display screen. Concrete surface crack measurement method by image processing. A distance measuring step of measuring a distance to an inspection object; A focus adjusting step of adjusting a focus of the camera according to the measured distance; A photographing step of photographing an image of the inspection target by the camera; An image display step of displaying the photographed image on a display screen; A length calculation step of calculating an actual length between a plurality of points in the image displayed on the display screen based on the distance measured in the distance measuring step; And A length display step of displaying the actual length on the display screen; The distance measuring step measures the distance to at least three points that do not form a straight line on the inspection object, An inclination angle calculation step of calculating an inclination angle of the inspection object with respect to the optical axis of the camera based on the calculated distances to the three points; And And a length correction step of correcting the distance calculated in the length calculation step based on the inclination angle. 10. The method of claim 9, wherein the image displaying step displays an image corrected based on the inclination angle on the display screen. A distance measuring step of measuring a distance to an inspection object; A focus adjusting step of adjusting a focus of the camera according to the measured distance; A photographing step of photographing an image of the inspection target by the camera; An image display step of displaying the photographed image on a display screen; A length calculation step of calculating an actual length between a plurality of points in the image displayed on the display screen based on the distance measured in the distance measuring step; And A length display step of displaying the actual length on the display screen; And a morphology step of applying a morphology technique to make the brightness of the background of the photographed image uniform. 12. The method of claim 11, wherein the morphology technique is a technique of subtracting the photographed image from the image of performing a closed operation on the photographed image.

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