US 8,553,971 B2Granted

Method and system for measuring object

AssigneeIndustrial Technology Research Institute

InventorsKuo-Tang Huang, Bor-Tung Jiang, Shang-Chieh Lu, Po-Huang Shieh

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Abstract

A method and system for measuring three-dimensional coordinates of an object are provided. The method includes: capturing images from a calibration point of known three-dimensional coordinates by two image-capturing devices disposed in a non-parallel manner, so as for a processing module connected to the image-capturing devices to calculate a beam confluence collinear function of the image-capturing devices; calibrating the image-capturing devices to calculate intrinsic parameters and extrinsic parameters of the image-capturing devices and calculate the beam confluence collinear function corresponding to the image-capturing devices; and capturing images from a target object by the image-capturing devices so as for the processing module to calculate three-dimensional coordinates of the object according to the beam confluence collinear function. In so doing, the method and system enable the three-dimensional coordinates and bearings of a target object to be calculated quickly, precisely, and conveniently. Hence, the method and system are applicable to various operating environments.

Claims19

Dependent claims

A method for measuring an object, by a first image-capturing device, a second image-capturing device not parallel thereto, and a processing module connected to the first and second image-capturing devices, the method comprising the steps of:

(1) capturing a first image and a second image of at least a calibration point of known three-dimensional coordinates by the first image-capturing device and the second image-capturing device, respectively;
(2) substituting parameters attributable to the first image and the second image, respectively, and corresponding to the at least a calibration point of known three-dimensional coordinates into a geometric function based on a beam confluence collinear imaging principle, and performing computation on the geometric function with a preset algorithm, so as to calculate a first lens distortion parameter, a first lens center, and a first bearings parameter of the first image-capturing device, and a second lens distortion parameter, a second lens center, and a second bearings parameter of the second image-capturing device, by the processing module, wherein the geometric function based on the beam confluence collinear imaging principle satisfies
x
c
=
-
f
⁡
[
m
11
⁡
(
X
A
-
X
L
)
+
m
12
⁡
(
Y
A
-
Y
L
)
+
m
13
⁡
(
Z
A
-
Z
L
)
m
31
⁡
(
X
A
-
X
L
)
+
m
32
⁡
(
Y
A
-
Y
L
)
+
m
33
⁡
(
Z
A
-
Z
L
)
]
y
c
=
-
f
⁡
[
m
21
⁡
(
X
A
-
X
L
)
+
m
22
⁡
(
Y
A
-
Y
L
)
+
m
23
⁡
(
Z
A
-
Z
L
)
m
31
⁡
(
X
A
-
X
L
)
+
m
32
⁡
(
Y
A
-
Y
L
)
+
m
33
⁡
(
Z
A
-
Z
L
)
]
with (XA, YA, ZA) denoting known three-dimensional coordinates of the calibration point (xc, yc) denoting coordinates of the image captured by the first or second image-capturing device from the at least a calibration point, f denoting a known focal length of the first or second image-capturing device, (X1, Y1, Z1) denoting the first or second lens center, and m11, m12, m13, m21, m22, m23, m31, m32 and m33 are parameters of the first or second image-capturing device, and;
(3) substituting the first lens distortion parameter, the first lens center, the first bearings parameter, the second lens distortion parameter, the second lens center, and the second bearings parameter thus calculated into the geometric function based on the beam confluence collinear imaging principle, so as to generate a first beam confluence collinear function and a second beam confluence collinear function which correspond to the first and second image-capturing devices, respectively, by the processing module.

145 more elements

(1) capturing a first image and a second image of at least a lens calibration point of known three-dimensional coordinates by the first image-capturing device and the second image capturing device, respectively, followed by calculating, with a lens calibration algorithm, a first lens distortion parameter of the first image-capturing device and a second lens distortion parameter of the second image-capturing device according to the first image and the second image, respectively, by the processing module;
(2) capturing image coordinates of a plurality of bearing calibration points of known three-dimensional coordinates by the first image-capturing device and the second image-capturing device likewise, followed by substituting the three-dimensional coordinates of the bearing calibration points, the first lens distortion parameter, and the second lens distortion parameter into a geometric function based on a beam confluence collinear imaging principle by the processing module, wherein the geometric function comprises an unknown first lens center and an unknown first bearings parameter of the first image-capturing device and an unknown second lens center and an unknown second bearings parameter of the second image-capturing device, wherein the geometric function based on the beam confluence collinear imaging principle satisfies
x
c
=
-
f
⁡
[
m
11
⁡
(
X
A
-
X
L
)
+
m
12
⁡
(
Y
A
-
Y
L
)
+
m
13
⁡
(
Z
A
-
Z
L
)
m
31
⁡
(
X
A
-
X
L
)
+
m
32
⁡
(
Y
A
-
Y
L
)
+
m
33
⁡
(
Z
A
-
Z
L
)
]
y
c
=
-
f
⁡
[
m
21
⁡
(
X
A
-
X
L
)
+
m
22
⁡
(
Y
A
-
Y
L
)
+
m
23
⁡
(
Z
A
-
Z
L
)
m
31
⁡
(
X
A
-
X
L
)
+
m
32
⁡
(
Y
A
-
Y
L
)
+
m
33
⁡
(
Z
A
-
Z
L
)
]
with (XA, YA, ZA) denoting known three-dimensional coordinates of the calibration point (xc, yc) denoting coordinates of the image captured by the first or second image-capturing device from the at least a calibration point, f denoting a known focal length of the first or second image-capturing device, (X1, Y1, Z1) denoting the first or second lens center and m11, m12, m13, m21, m22, m23, m31, m32 and m33 are parameters of the first or second image-capturing device, and;
(3) performing computation on the geometric function with a preset algorithm so as to calculate the first lens center and the first bearings parameter of the first image-capturing device and the second lens center and the second bearings parameter of the second image-capturing device, followed by substituting the first lens center, the first bearings parameter, the second lens center, and the second bearings parameter thus calculated into the geometric function based on the beam confluence collinear imaging principle so as to generate a first beam confluence collinear function and a second beam confluence collinear function which correspond to the first and second image-capturing devices, by the processing module.

145 more elements

A system for measuring an object, comprising:

a first image-capturing device and a second image-capturing device not parallel thereto, the first and second image-capturing devices being configured to capture images of a target object and a calibration point;
a processing module connected to the first and second image-capturing devices for calibrating a lens and measuring an object according to the images captured from the calibration point by the first and second image-capturing devices, wherein the processing module substitutes parameters of the images captured from the calibration point into a geometric function based on a beam confluence collinear imaging principle so as to perform computation on the geometric function with a preset algorithm and thereby calculate a first lens distortion parameter, a first lens center, and a first bearings parameter of the first image-capturing device and a second lens distortion parameter, a second lens center, and a second bearings parameter of the second image capturing device, followed by capturing feature-point coordinates of the target object by the first image-capturing device and the second image-capturing device concurrently, and further followed by substituting the feature-point coordinates, the first lens distortion parameter, the first lens center, the first bearings parameter, the second lens distortion parameter, the second lens center, and the second bearings parameter thus captured by the first and second image-capturing devices into the geometric function based on the beam confluence collinear imaging principle so as to calculate three-dimensional coordinates of the target object;
a first rotating mechanism for connection with the first image-capturing device;
a second rotating mechanism for connection with the second image-capturing device;
and
a stationary base for connection with the first and second rotating mechanisms,
wherein the first and second rotating mechanisms are movably disposed on the stationary base and configured to adjust an angle of rotation of the first and second rotating mechanisms according to three-dimensional coordinates of the target object and/or the calibrating point, so as for the first and second image-capturing devices to be disposed on the stationary base in a non-parallel manner.

4 more elements

Dependencies are inferred from the claim text.