JP2003035536A - Compensation method in image processing displacement measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a highly precise displacement measurement to be acquired. SOLUTION: A compensation method is applied, when collimating an excavating cross section 18 with time at the same measuring point X through a digital camera 12 to acquire the picked-up image data and determining an interior space displacement with time of the excavating cross section 18 by operation based on a plurality of the acquired picked-up image data. Based on rotation angle θ in a horizontal in-plane, elevation angle ϕ in a perpendicular in-plane, and optical-axis rotation angle γ when installing the digital camera 12 at the measuring point X, the picked-up image data is compensated and a displacement is calculated by using the picked-up image data after compensation. Three standard points 201 , 202 , 203 are imaged into the picked-up image data, of which the absolute position-coordinate values are known, and the compensation of the displacement is determined by solving simultaneous equations from the image processing data of these three standard points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction method in image processing displacement measurement, and particularly to a method for measuring displacement when image processing data is acquired over time using a digital camera and the displacement is measured based on this data. The present invention relates to a technique for improving accuracy.

[0002]

2. Description of the Related Art Measurement by image processing using a digital camera such as a CCD is used for inspection of industrial products, processing control, etc., and is mainly used in fields where a high degree of measurement accuracy is not required.

By the way, recently, it has been attempted to apply the measurement by such image processing to the measurement of the inner sky displacement of the tunnel excavation surface, and one example thereof is, for example, Japanese Patent Laid-Open No. Hei 2
No. 000-329554.

In the method for measuring the displacement in the tunnel using the image processing disclosed in this construction method, a plurality of image points that can be imaged are set along the excavation cross section to be measured, and these point images are taken over time. Then, a plurality of pieces of image processing data are obtained, a movement amount between the same reference points is calculated from the image processing data, and this is grasped as a temporal displacement of the inner sky.

However, the displacement measurement utilizing such image processing has the following technical problems.

[0006]

That is, in the displacement measurement of the inside of the tunnel as described above, it is necessary to photograph the reference points from the same place a plurality of times with the digital camera in accordance with the progress of the cutting face. But at the tunnel excavation site,
If you always install a camera in the shooting location, it will obstruct traffic such as heavy equipment and other work, so normally, every time you shoot, install the camera in the same location and aim in the same direction. It will be done in the same way.

In this case, the installation location of the camera can be reproduced fairly accurately by a surveying instrument or the like, but it is very difficult to reproduce the same state in the collimation direction of the camera, which is almost impossible.

However, if the collimation direction of the camera is slightly different each time the image is taken, the position of the imaged gage mark changes slightly, which causes a measurement error when measuring a minute displacement. As a result, there has been a problem that the measurement accuracy becomes low.

The present invention has been made in view of the above conventional problems, and an object thereof is to correct an error factor based on a difference in the collimation direction of a camera to achieve high accuracy. An object of the present invention is to provide a correction method in image processing displacement measurement that enables the measurement of

[0010]

In order to achieve the above object, the present invention is directed to collimate an object to be measured from the same measurement point with a digital camera over time to acquire imaged image data, and to acquire a plurality of acquired image data. In the image processing displacement measurement for measuring the displacement of the measured object over time based on the imaging screen data, the rotation angle in the horizontal plane and the vertical plane when the digital camera is installed at the measurement point. The captured image data is corrected based on the elevation angle and the rotation angle of the optical axis, and the displacement is calculated based on the corrected captured image data.

According to the correction method in the image processing displacement measurement configured as described above, when the digital camera is installed at the measurement point, based on the rotation angle in the horizontal plane, the elevation angle in the vertical plane, and the optical axis rotation angle, Since the captured image data is corrected and the displacement is calculated from the corrected captured image data, the displacement measurement can be performed with high accuracy.

The rotation angle in the horizontal plane, the elevation angle in the vertical plane,
The correction of the displacement based on the optical axis rotation angle is performed by capturing three standard points whose absolute position coordinate values are known in the captured image data,
It can be obtained by solving simultaneous equations from the image processing data of these three standard points.

The object to be measured is an excavated tunnel inner air section, and a plurality of imaging targets that can be imaged are installed along the inner air section and applied to the tunnel inner air displacement measurement. You can

The three standard points may be laser beams for surveying assistance that are constantly radiated from the tunnel pit side toward the face.

The measurement target includes a target main body whose lower end side is embedded in the inner cross section, a light receiving sensor which is installed on a visible surface of the target main body, and operates by receiving a predetermined light, and the light receiving unit. It can be configured with a light emitting element that emits light for a predetermined time by the operation of the sensor.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 1 to 6 show an embodiment of a correction method in image processing displacement measurement according to the present invention.

The correction method shown in FIG.
The case where the image processing measurement is applied to the measurement of the in-air displacement of the excavated cross section of the tunnel 10 is shown. When measuring the inner air displacement of the tunnel 10 by image processing, the digital camera 12
, A plurality of image pickup screens A, B ... Taken by this digital camera 12 are input and displayed on the monitor 14, or a plurality of image pickup screens A, B .. A personal computer 16 that performs image processing is used.

In this embodiment, the personal computer 16 is installed at the tunnel construction site.
It may be installed in an office to exchange information wirelessly or by wire, or the image data of the camera 12 may be written in a recording medium and the personal computer 16 itself may be transported to another place. .

When measuring the inner-air displacement, an excavation section 18 to be measured is set immediately before the face 17 immediately after excavation, and a plurality of measurement targets 20 are installed on the excavated section 18.

The measurement target 20 can be imaged by the digital camera 12, and an example thereof is shown in FIGS. The measurement target 20 shown in these figures includes a target body 20a and a light receiving sensor 20b.
And a light emitting element 20c. Target body 2
0a includes a hollow cylindrical tubular body 200a and a hermetic stopper 201a.

A control circuit component, a battery power source, and the like, which will be described later, are housed in the cylindrical body 200a and are closed by a hermetic plug 201a. The end of the target body 20a on the closed side of the tubular body 200a is embedded in the excavated cross section 18.

The light receiving sensor 20b is, for example, a predetermined light,
For example, a CdS cell, a phototransistor, or the like that operates by receiving infrared light is formed, and is arranged on the visible surface of the cylindrical body 200a.

The light emitting element 20c is composed of, for example, a light emitting diode that emits infrared light, and is arranged on the end surface side of the cylindrical body 200a and on the side of the light receiving sensor 20b. In the case of the present embodiment, the light emitting element 20c is configured to start light emission by the operation of the light receiving sensor 14 and then emit light for a predetermined time.

FIG. 6 shows an example of a drive control circuit 20d for causing such light emission. The drive control circuit 20d shown in this figure is housed and installed in the cylindrical body 200a of the target body 20a.

In the drive control circuit 20d shown in the figure, a light receiving sensor 20b and a light emitting element 20c are connected in series, and a timer circuit 20e and a power supply battery 20f are connected in series to the other end of the light emitting element 20c. There is.

The ON time of the timer circuit 20e in this case is set to a time required for measurement, for example, about 5 to 10 minutes. Further, the light receiving sensor 20b is connected in parallel with a self-holding circuit 20g that maintains an electrically connected state by its operation, and is connected to the negative electrode side of the power supply battery 20f.

Measurement target 20 with digital camera 12
When the image is captured, the light receiving sensor 20b is irradiated with light by, for example, a flashlight or a strobe.

When the light receiving sensor 20b is irradiated with light, the light receiving sensor 20b is in an operating state, and as shown in FIG.
Since it has the self-holding circuit 20g, the operating state of the light receiving sensor 20b is maintained as it is even if the light irradiation is stopped.

When the light receiving sensor 20b is activated, the power of the power supply battery 20f is applied to the light emitting element 20c via the timer circuit 20e, whereby the light emitting element 20c self-luminesces.

The light emitting state of the light emitting element 20c is as follows.
It continues while the timer circuit 20e is in the operating state, and when the set time has elapsed and the timer circuit 20e is in the non-operating state, the self-emission of the light emitting element 20c disappears.

Therefore, when the digital camera 12 is collimated in that direction while the light emitting element 20c is emitting light, the information necessary for image processing is obtained. The installation state of the measurement target 20 is set to a position separated from the excavation wall surface 18 by the same distance.

The measurement target 20 is not limited to the above configuration, and may be, for example, a reflection plate that reflects and emits light when irradiated with light, a light emitting diode that emits light by itself, a penlight, or the like.

On the other hand, in the case of the present embodiment, three standard points 22 ₁ , 22 ₂ and 22 ₃ used for correction of displacement, which will be described later, are installed along with the installation of such a measurement target 20.

As will be described later, these standard points 22 ₁ , 22 ₂ , and 22 ₃ have known absolute position coordinate values that do not change depending on the location. In the case of this embodiment, the excavated cross section of the tunnel 10 is used. The laser light L is set at three positions on both sides of and in the center upper part, and the laser light L is always radiated from the wellhead side of the tunnel 10 toward the facet 17.

The three laser lights L are, for example, those which emit red light, and three laser light generators 24 are fixedly installed at a predetermined position in front of the face face 17 to generate the laser lights. The laser light L is always projected from the device 24 toward the face 17 on the same position.

Such a laser beam L is used, for example, as a reference when measuring the position of the face face 17, and when measuring the displacement of the excavation section 18, a screen is displayed on the excavation section 18 to be measured. 26 is installed and the laser light L is blocked by the screen 26, so that the laser light L is emitted on the screen 26 to enable imaging.

When the measurement target 20 and the three standard points 22 ₁ , 22 ₂ and 22 ₃ are installed as described above,
The digital camera 12 is supported on a tripod at a predetermined measurement point X, and collimation photography is performed in a state in which these are simultaneously included, and an image pickup screen A immediately after excavation is picked up.

The image pickup screen A photographed by the digital camera 12 is stored in the memory of the personal computer 16 or the like, taken out as needed, and can be displayed on the monitor 14. FIG. 4A shows an example of the image pickup screen A displayed on the monitor 14.

In the figure, what is indicated by X is an image of the measurement target 20, and what is enclosed by a square is an image of 3 standard points 22 ₁ , 22 ₂ , and 22 ₃ . Also,
The semicircular curve shown in the figure is obtained by calculating the inner peripheral surface of the excavation section 18 to be measured from the installation position of each measurement target 20 and displaying it.

FIG. 3 shows the relationship between the digging section 18 to be measured, the face 17 and the subsequent digging state when the image pickup screen A is photographed. Measurement target excavation section 18
Is set immediately before the face 17 is excavated.

Then, as shown in the same figure, when the excavation of the face 17 progresses with the passage of time and the point B is reached from the point where the image pickup screen A is obtained, the digital camera 12 causes the section to be excavated again to be measured. 18 shots are taken.

The photographing at this time is similar to the case described above.
The digital camera 12 is installed on the measurement point X, and the measurement target 20 and the three standard points 22 ₁ , 22 ₂ , and 22 ₃ are photographed so as to collimate in substantially the same direction.

FIG. 4B shows an example of the image pickup screen B obtained by such collimation photography. This imaging screen B
Also, in the above, the image indicated by X is the image of the measurement target 20, and the image in which X is enclosed by a square is 3 standard points 22 ₁ ,
22 ₂ and 23 ₃ . In this way, the imaging screen A immediately after excavation and the imaging screen B after a predetermined time has elapsed
Is obtained, the image pickup screens A and B are superposed. When the image pickup screens A and B are superposed, the three standard points 22 ₁ , 22 ₂ and 22 ₃ are photographed on the image pickup screens A and B, so that they are matched with each other.

FIG. 4C shows a state in which the image pickup screens A and B are superposed on the monitor 14 after the image processing. When such an overlay screen is obtained, by obtaining the amount of movement between the corresponding measurement targets 20,
The in-air displacement of the excavated cross section 18 on each measurement target 20 can be known.

Then, the excavation further progresses, and the imaging screen B
When reaching point C from the point where the
2, the image of the excavation section 18 to be measured is taken again,
The obtained image pickup screen C and either one or both of the image pickup screens A and B are superposed, and the inner-air displacement of the excavation cross section 18 is obtained in the same manner as above.

However, in such image processing displacement measurement, as described above, an error factor based on the difference in the collimation direction of the digital camera 12 is included, and the measurement accuracy is lowered.

Therefore, in this embodiment, the following correction method is adopted. Here, first, the error factor based on the difference in the collimation direction of the digital camera 12 will be described more specifically.

FIGS. 7 to 9 show examples of error factors which are generated based on the difference in the collimation direction of the digital camera 12. When taking a picture of the measurement target 20 or the like with the digital camera 12, the camera 12 is installed at the measuring point X. At that time, if the collimation direction of the camera 20 is different from that at the time of the previous taking, The difference can be indicated by a rotation angle θ (pan angle) in the horizontal plane of the camera 12, an elevation angle φ in the vertical plane, and an optical axis rotation angle γ, as shown in FIG. 7.

FIG. 8 shows a case in which the pan angle θ is different. When the pan angle θ is different from that in the previous photographing, the black point originally photographed by a black circle is photographed at the position of X. However, the difference between these causes a measurement error factor.

FIG. 9 shows a case where there is a difference in elevation angle φ. When the elevation angle φ is different from that in the previous photographing, the black point originally photographed by the black circle is photographed at the position of X, and that point is photographed. result,
The height h becomes h ', which causes a measurement error due to the deviation of the height h from the front.

Although the optical axis rotation angle γ does not directly cause a measurement error, it may be a measurement error factor due to image distortion or the like. Therefore, in the present embodiment, this correction is also taken into consideration. is doing.

If there are three known points in the image data picked up by the digital camera 12, the error factors based on the difference in the collimation direction of the digital camera 12 are as follows.
Since these can be calculated, in the present embodiment, the three standard points 22 ₁ , 22 ₂ , and 22 ₃ corresponding thereto are photographed.

When calculating the rotation angle θ (pan angle) in the horizontal plane, the elevation angle φ in the vertical plane, and the optical axis rotation angle γ, which are error factors, based on the difference in the collimation direction of the camera 12, FIG. As shown in, the absolute position coordinate system that does not change depending on the location, for example, the world coordinate system (x, y, z), and the optical axis direction of the digital camera 12 installed on the measurement point X is the Y axis. Assume a camera coordinate system (X, Y, Z).

The world coordinate system (x, y, z)
Is, in a broad sense, a coordinate system with the center of the earth as the origin, but in the case of the present embodiment, the coordinate values do not change with the progress of the face, for example, the wellhead that is the starting point of tunnel excavation. It is a coordinate system whose origin is a point with a part.

Then, the image plane I (uv
Face). In this case, the distance from the center of the optical axis to the image plane I corresponds to the focal length of the digital camera 12,
This is Df.

The absolute coordinate of the position of the camera 12 is O
If (xc, yc, zc), the world coordinate system (x,
The position coordinate P (u, Df, v) of the camera 12 on the u-v plane imaged in y, z) is

[Formula 1] Can be expressed as Here, θ is the pan angle of the camera, φ is the elevation angle, γ is the rotation angle with respect to the optical axis, and is the world coordinate system (x, y, z) and the camera coordinate system (X, Y, Z). The coordinate transformation of is represented by a simple rotation matrix.

Here, if the parameters of the position and orientation of the camera 12 are S = (xc, yc, zc, θ, φ, γ), on the image of the point (x, y, z) on the world coordinate system. Point (u, v) is u = u (x, y, z, S), v = v
It can be written as (x, y, z, S).

Using this equation, the six unknowns of S (x
In order to obtain c, yc, zc, θ, φ, γ), six equations are required. Therefore, in this embodiment, the world position coordinate value is known and the camera coordinate system (X,
3 standards that can calculate the coordinate values of Y, Z) 2
2 ₁ , 22 ₂ and 22 ₃ are capable of being photographed by the camera 12.

When such known coordinate values are included in the captured image, the following six equations can be obtained from the captured image data.

[Formula 2]

This equation is obviously a non-linear simultaneous equation and can be solved as it is, but Newton-R
An approximate solution can be obtained by the aphson method.
That is, in the Newton-Raphson method, as shown in FIG.
As shown in 1, the solution of equation f (x) = 0 is

[Formula 3] It is given by the recurrence formula of.

Extending this to simultaneous equations, simultaneous equations

[Formula 4] Is the solution

[0062]

[Formula 5] Given by the recurrence formula of
= (Xc, yc, zc, θ, φ, γ) is obtained.

As described above, the camera parameter S =
When (xc, yc, zc, θ, φ, γ) are respectively obtained, the imaging screens A and B are obtained based on these parameters.
The position coordinates of the measurement target 20 are corrected respectively, and thereafter, the measurement targets 20 are superposed as shown in FIG.
Calculate the in-air displacement of.

According to the correction method configured as described above, the rotation angle θ in the horizontal plane, the elevation angle φ in the vertical plane, which are the error factors due to the difference when the digital camera 12 is installed at the measurement point X, Since the position coordinates of the measurement target 20 are corrected based on the optical axis rotation angle γ and the displacement is calculated based on the correction value, displacement measurement can be performed with high accuracy.

In the above embodiment, the case where the correction method of the present invention is applied to the measurement of the in-air displacement of the excavated cross section of the tunnel 10 has been exemplified, but the present invention is, for example, a cavity for construction of an underground power plant. It can also be applied to displacement measurement of parts.

[0066]

As described above in detail, according to the present invention, according to the correction method in the image processing displacement measurement,
By correcting the error factor based on the difference in the collimation directions of the cameras, highly accurate measurement becomes possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an implementation state when measuring an inner sky displacement of a tunnel excavation cross section to which a correction method in image processing displacement measurement according to the present invention is applied.

FIG. 2 is an explanatory diagram of an image reproduced by capturing an image of the measurement object shown in FIG. 1 with a digital camera.

FIG. 3 is an explanatory diagram showing the progress of excavation of the tunnel shown in FIG. 1.

FIG. 4 is an explanatory diagram when superimposing a plurality of image pickup screens photographed by the measuring method according to the present invention.

5 is an external perspective view showing an example of a measurement target used in the measurement method shown in FIG.

6 is a circuit diagram of an electric system of the measurement target of FIG.

FIG. 7 is an explanatory diagram of an error factor based on a difference in collimation directions of cameras to be corrected by the correction method of the present invention.

FIG. 8 is a detailed explanatory diagram in the case of the pan angle of the error factor shown in FIG. 7.

9 is a detailed explanatory diagram in the case of an elevation angle of an error factor shown in FIG.

FIG. 10 is an explanatory diagram of a coordinate system assumed by the correction method of the present invention.

FIG. 11 is an explanatory diagram of an approximate expression used in the correction method according to the present invention.

[Explanation of symbols]

10 tunnel 12 digital camera 14 monitor 16 personal computer 18 measurement target excavation cross section _{201 1-3} standard point 22 measurement target 24 laser light generator

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G06T 1/00 300 G06T 3/00 200 3/00 200 7/20 B 7/20 G01B 11/24 K ( 72) Inventor Shuji Hashimoto 1-13-19 Hachiman, Ichikawa-shi, Chiba F-term (reference) 2F065 AA04 CC40 FF04 GG04 GG07 JJ03 JJ26 QQ17 QQ24 RR07 SS02 5B057 AA01 AA19 BA11 CD12 DC09 DC32 5L096 BA02 CA04 DA02 HA04 MA69

Claims (5)

[Claims] 1. An object to be measured is temporally collimated with a digital camera from the same measurement point to acquire captured image data, and the object to be measured over time is acquired based on the acquired plurality of imaging screen data. Image processing displacement measurement for measuring the actual displacement, based on the rotation angle in the horizontal plane, the elevation angle in the vertical plane, and the optical axis rotation angle when the digital camera is installed at the measurement point, the captured image data is A correction method in image processing displacement measurement, wherein the displacement is calculated based on the corrected captured image data. 2. The correction of the displacement based on the rotation angle in the horizontal plane, the elevation angle in the vertical plane, and the optical axis rotation angle captures three standard points of which absolute position coordinate values are known in the captured image data. The correction method in image processing displacement measurement according to claim 1, wherein the correction method is obtained by solving simultaneous equations from the image processing data of the three standard points. 3. The object to be measured is an excavated tunnel inner air section, and a plurality of image-capable measurement targets are installed along the inner air section. 2. The correction method in the image processing displacement measurement described in 2. 4. The correction method in image processing displacement measurement according to claim 3, wherein the three standard points are laser beams for surveying assistance that are constantly radiated from the tunnel pit side toward the face. . 5. The measurement target includes a target main body whose lower end side is embedded in the inner cross section, a light receiving sensor which is installed on a visible surface of the target main body, and operates by receiving a predetermined light. The correction method in image processing displacement measurement according to claim 3, further comprising a light emitting element that emits light for a predetermined time by the operation of the light receiving sensor.