JP2009243984A - Calibration data generation method, calibration data generation device, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for acquiring calibration data necessary for performing three-dimensional measurement, even when a photographing range is wide. <P>SOLUTION: This method for generating calibration data when executing stereo photographing by using a plurality of cameras installed at each different angle to a subject includes a rod erection process for erecting a calibration rod having a prescribed length, vertically on a place wherein an absolute position is predetermined in a photographing domain of the cameras; a photographing process for photographing by the cameras, the calibration rod erected in the rod erection process; and an upper and lower end specification process for specifying each position of upper and lower ends of the calibration rod in photographed data photographed in the photographing process. Hereby, each position of the upper and lower ends of the calibration rod on at least four spots in the photographed data is predetermined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for obtaining calibration data by creating a calibration reference point for measuring a three-dimensional position by photographing a subject in stereo, a calibration data creation device, and a computer program used for calibration data creation. .

Stereo image processing technology for photographing a single subject from different angles and executing three-dimensional data processing from the image data is used in various fields. For example, as shown in FIG. 7, a cube whose size is known in advance is stereo-photographed and used for three-dimensional data correction.
For example, the technique described in Patent Document 1 is provided.
JP-A-9-210694

  This technology realizes a three-dimensional measuring apparatus capable of “excluding errors due to artificial operations and improving surveying accuracy” (see FIG. 8).

Further, as a technique for improving the efficiency of a wide imaging range in non-contact three-dimensional measurement, there is a technique described in Patent Document 2.
JP 2007-101275 A

  Now, if the shooting range is very wide, the error will increase if the calibration cube is not large. It was difficult to prepare a large cube in advance, and there was no appropriate method for forming it on site. Even if the techniques of Patent Documents 1 and 2 are used or they are combined, the technique has not reached a practical level.

The problem to be solved by the present invention is to provide a technique for enabling acquisition of calibration data necessary for three-dimensional measurement even when the photographing range is wide.
An object of the present invention is to provide a method for enabling acquisition of calibration data necessary for three-dimensional measurement even when the imaging range is wide.
The object of the present invention is to provide an apparatus for enabling acquisition of calibration data necessary for three-dimensional measurement even when the photographing range is wide.
An object of the invention described in claim 4 is to provide a computer program for enabling acquisition of calibration data necessary for three-dimensional measurement even when the photographing range is wide.

  In order to solve the above problem, it is assumed that a stick whose length is known in advance is set up and photographed. The absolute position of the point where the bar is erected is specified, and the absolute position of the upper end is determined from this and the length of the bar, and is used as basic data for three-dimensional measurement.

(Claim 1)
The invention according to claim 1 relates to a method for creating calibration data when performing stereo shooting using a plurality of cameras installed at different angles with respect to a subject.
That is, a rod erecting step in which a calibration rod having a predetermined length is erected vertically in a position where the absolute position is specified in the imaging area of the camera, and a calibration erecting in the rod erecting step A shooting step of shooting the working rod with the camera, and an upper and lower end specifying step of specifying the positions of the upper and lower ends of the calibration rod in the shooting data shot in the shooting step. It is characterized in that the positions of the upper and lower ends of the calibration bar in at least four places are specified.

(Glossary)
The “calibration bar” refers to a bar having a length and thickness that have a presence even in shooting data in a wide shooting range. It is preferable to provide light emitting elements or the like at both ends so that the positions of both ends of the rod can be easily understood in the photographing data.
For specifying the “absolute position”, for example, GPS is used. The calibration rod may be equipped with GPS, or the camera may be equipped with GPS, and the distance from the camera may be measured in specifying the position of the calibration rod.

(Function)
A calibration rod having a predetermined length is erected vertically in the imaging region of the camera by the rod erection process. Then, the calibration rod set up is photographed with the camera. The positions of the upper and lower ends of the calibration rod in the photographed photographing data are specified in the upper and lower end specifying step. By using a predetermined location where the length and absolute position of the calibration rod are specified, the positions of the upper and lower ends of the calibration rod in the photographing data can be specified. By repeating the process up to the upper and lower end identification process until the upper and lower end positions of the calibration rod are specified at least at four locations in the imaging data, if a total of eight points of 3D data is obtained, a rectangular parallelepiped can be used using them. Can be formed. The eight points serve as basic data for executing three-dimensional calibration on image data acquired by stereo imaging. Since the size for obtaining the eight-dimensional three-dimensional data can be freely set, basic data with a small error can be acquired even in a wide imaging region.

(Claim 2)
The invention according to claim 2 relates to an apparatus for creating a calibration reference point when performing stereo shooting using a plurality of cameras installed at different angles with respect to a subject.
That is, a calibration bar having a predetermined length in the imaging area of the camera is vertically erected at a position where the absolute position is specified, and the erection means is vertically erected by the rod erection means. Upper and lower end specifying means for specifying the positions of the upper and lower ends of the calibration bar in the shooting data obtained by shooting the calibration bar with the camera, and a bar for moving the bar standing means within the shooting area of the camera Moving means; calibration data creating means for creating calibration data using position data of the upper and lower ends at least at four locations in the photographic data among the upper and lower end position data specified by the upper and lower end specifying means; , Provided.

(Claim 3)
The invention described in claim 3 limits the calibration data creation device according to claim 2,
The bar erecting means includes vertical determination means for determining whether or not the calibration bar erects vertically.

(Glossary)
“Vertical judgment means” is, for example, a level. If digital output is possible for the bar erecting means, fine adjustment can be quickly performed in erecting when the output is not vertical.

(Claim 4)
The invention according to claim 4 relates to a computer program for creating a calibration reference point when performing stereo shooting using a plurality of cameras installed at different angles with respect to a subject.
The program includes: a bar standing procedure for confirming that a calibration rod having a predetermined length is vertically set in the photographing area of the camera; and a calibration rod that is set up by the rod standing procedure. A shooting data acquisition procedure for acquiring shooting data by shooting with the camera, and an upper and lower end specification procedure for specifying the positions of the upper and lower ends of the calibration rod in the shooting data acquired by the shooting data acquisition procedure. Further, the computer program causes the computer to execute calibration data creation procedures for creating calibration data using the upper and lower end position data in at least four positions in the upper and lower end position data.

  According to the first to fourth aspects of the present invention, an apparatus and a method for enabling acquisition of calibration data required for accurate three-dimensional measurement even when the photographing range of a subject is wide. And could provide computer programs.

  Hereinafter, the present invention will be described in more detail based on embodiments and drawings. The drawings used here are FIGS. 1 to 6. 1 to 3 show a first embodiment, and FIGS. 4 to 6 show a second embodiment.

(First embodiment)
A first embodiment will be described with reference to FIG.
First, two cameras for stereo shooting are installed (step 1). Then, a background image is taken (step 11). The calibration rod is moved to a place where the position data can be specified in advance in the imaging area of the camera and installed vertically (steps 2 and 3). Then, the vertical calibration rod is photographed at the photographing angle of the background image (step 4). That is, at the same shooting angle, image data that does not contain a calibration rod and image data that contains it are acquired.

If the difference between the shooting data containing the calibration bar and the background-only shooting data is obtained, image data of only the calibration bar can be obtained (step 42). The difference image data is also temporarily saved (step 43). Then, the sum total of the difference image data already stored is calculated (step 44). The length of the calibration bar is determined in advance, and the absolute position data can be specified, so that the reference length can be set in the image data containing the calibration bar.
Since the position data of the calibration bar is required at four or more locations, if it is not sufficient, the operation from step 2 is repeated (step 6). If it is sufficient, the flow is terminated and data of only the calibration rod can be obtained.

Further description will be given with reference to FIGS. 2 and 3.
It is assumed that the luminance information of the photographing data in which the calibration bar is not on the screen is represented by g0 (X, Y). The luminance information in the first calibration rod shooting data is g1 (X, Y), the luminance information in the second calibration rod shooting data is g2 (X, Y), and in the third calibration rod shooting data. The luminance information is g3 (X, Y) and the luminance information in the fourth calibration rod shooting data is g4 (X, Y).
When the background image is subtracted, the luminance information of the shooting data of the first calibration rod is G1 | g0-g1 |. Similarly, the brightness information of the shooting data of the second calibration bar is G2 | g0-g2 |, the brightness information of the shooting data of the third calibration bar is G3 | g0-g3 |, and the brightness information of the fourth calibration bar. The luminance information of the shooting data is G4 | g0-g4 |.

  As shown in FIG. 3, G1, G2, G3, and G4 indicate luminance differences from the background, and the maximum luminance at each position of the image is extracted from them, and the sum data, that is, Gcalib = Max {G1 ~ G4} image is created. That is, in the G1 to G4 images, if the background is luminance = 0 and the luminance of each calibration bar is 5, the luminance = 5 at the position of the four calibration bars in the total data. Since the brightness of the calibration bar of 5 is the maximum, this is extracted from G1 to G4, respectively, and a Gcalib image is created. Using this calculation result, three-dimensional calibration data can be created.

Next, a second embodiment will be described with reference to FIGS.
In this embodiment, the length of the calibration rod and the position data of the four points where the calibration rod is raised are determined in advance, and the four calibration rods are stood up and photographed at a time to create the calibration data. It makes it easy.
In the first embodiment, step 11 and steps 42 to 44 can be omitted, and step 6 can also be omitted.

This will be described in more detail with reference to FIGS.
M1, m2, m3, and m4 shown in FIG. 5 are determined in advance as places where the calibration rods are set up vertically, and their absolute positions are determined using GPS or the like. The position of the place may be determined as a relative position to the camera.
A calibration rod is set up vertically at points m1, m2, m3, and m4, and images are taken with two cameras. Since four calibration bars can be prepared, photographing data can be obtained by setting the calibration bars on m1, m2, m3, and m4 at a time.

The tips of the calibration rods at m1, m2, m3, and m4 are d1, d2, d3, and d4, respectively, and a rectangular parallelepiped having apexes at m1 to m4 and d1 to d4 can be formed. Since it is a rectangular parallelepiped whose side length is known in advance, if it is used together with the absolute position data of m1, m2, m3, and m4, three-dimensional calibration data can be created. In addition, it is desirable to provide a light emitting element or the like at the tip of the calibration bar so that d1, d2, d3, and d4 can be clearly specified in the photographing data.
According to the first and second embodiments as described above, since the size for obtaining the three-dimensional data can be set freely in advance, basic data with a small error can be acquired even in a wide imaging region.

  The present invention can be used in industries that require stereo photography, for example, in the field of software creation such as measurement and image processing, in the fields of construction and civil engineering.

It is a flowchart which shows 1st embodiment. It is a conceptual diagram which shows 1st embodiment. It is a conceptual diagram which shows 1st embodiment. It is a flowchart which shows 2nd embodiment. It is a conceptual diagram which shows 2nd embodiment. It is a conceptual diagram which shows 2nd embodiment. It is a conceptual diagram which shows a prior art. It is a conceptual diagram which shows a prior art

Explanation of symbols

d1, d2, d3, d4; calibration rod tips m1, m2, m3, m4;

Claims (4)

A method for creating calibration data when performing stereo shooting using a plurality of cameras installed at different angles to a subject,
A rod erecting step for vertically erecting a calibration rod of a predetermined length within a shooting area of the camera to a place where the absolute position is specified;
A photographing step of photographing with the camera the calibration rod erected in the rod erection step;
By including an upper and lower end specifying step that specifies the positions of the upper and lower ends of the calibration rod in the shooting data shot in the shooting step,
A calibration data generation method characterized in that the positions of the upper and lower ends of a calibration bar at least at four locations in the photographing data are specified. An apparatus for creating a calibration reference point when performing stereo shooting using a plurality of cameras installed at different angles to a subject,
A rod erecting means for erecting a calibration rod of a predetermined length vertically in a position where the absolute position is specified in the imaging region of the camera;
Upper and lower end specifying means for specifying the positions of the upper and lower ends of the calibration rod in the photographing data obtained by photographing the calibration rod vertically set by the rod standing means;
A bar moving means for moving the bar erecting means within the imaging area of the camera;
Calibration data creating means for creating calibration data using the position data of the upper and lower ends in at least four locations in the photographing data among the position data of the upper and lower ends specified by the upper and lower end specifying means; A calibration data creation device characterized by that.   3. The calibration data creating apparatus according to claim 2, wherein the bar erecting means includes vertical determination means for determining whether or not the calibration bar is erect vertically. A computer program for creating a calibration reference point when performing stereo shooting using a plurality of cameras installed at different angles to a subject,
The program includes a bar erecting procedure for confirming that a calibration bar of a predetermined length is erect vertically to a place where the absolute position is specified in the shooting area of the camera,
An imaging data acquisition procedure for obtaining imaging data by imaging the calibration rod, which has been confirmed to be established by the rod installation procedure, with the camera;
Upper and lower end specifying procedure for specifying the positions of the upper and lower ends of the calibration rod in the shooting data acquired in the shooting data acquisition procedure,
A computer program that causes a computer to execute calibration data creation procedures for creating calibration data using the upper and lower position data in at least four locations in the photographed data among the identified upper and lower position data .

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